Executive summary 3 introduction 5
|
|  Yüklə 0.67 Mb.
|
|
Over diagnosis of malaria is a common feature of malaria in Zimbabwe (Freeman 1993b), and in the data peaks can be seen that do not lie within the known malaria season such as July 1990. The fact that the high cases of clinical malaria occur in January to May reflect actual malaria cases are confirmed by the few blood slide records which are found at Mutoko Hospital, though in general positivity rates are rarely more than 50%, and no slide records have been seen for any year prior to 1992 (Appendix Ten). The most important question in the malaria epidemiology of an area is whether the malaria parasite and vector mosquito survive the winter within the district. Only one indication exists of this where positive slides are recorded at Mutoko Hospital from Nyamazuwa Clinic in September and October of 1993. However, to confirm this point, it would be necessary to know if any of these cases were children (who are more likely to get malaria from home) or whether adult cases which had been followed up to see if they had travelled out of the district. However, it is unlikely that this question can be resolved for the moment as no blood slide submission forms for these cases could be found either at the district hospital or Nyamazuwa Clinic. The last bit of evidence to suggest that the area was once problematic in terms of malaria is that the area was sprayed for many years with DDT. However, this stopped in 1990/1 when the area was finally sprayed with Cislin (deltamethrin). Until further records are found, the reason for the residual house spraying programme cannot be known. It is also unfortunate that when the National Malaria Prevalence survey takes place Mutoko District is left out. Survey points occur in Mudzi which is a known malaria area, and in Goromonzi which is a known non malarial area. Logically, if such an exercise is carried out again more would be gained by surveying Mutoko than either Mudzi or Goromonzi. Possible Past Outbreaks Only one set of records were found prior to 1989 and that was from Makosa Clinic where T5 records suggested that there might have been a serious malaria outbreak in the district in 1988. However, no other data was found to confirm this one way or another. The Present Outbreak General Information The outbreak of malaria at Kawere Clinic was reported by the clinic when an abnormally high number of clinical cases of malaria appeared in March of this year (Table Two). TABLE TWO
Thereafter district and provincial staff visited the area and the following actions were taken. Blood Slides That malaria was in the area was established by a microscopist stationed at Kawere who examined 458 slides of which 229 were positive. However, the actual details of these slides is not known as the blood slide submission forms were not found. All further discussion is based on clinical assessment only which is fraught with problems. Residual House Spraying The whole of Kawere Ward, and parts of Mbudzi A, Mbudzi B and Musanhi Wards were sprayed with Fendona (alphacypermethrin) from April 1 - 17 1994. Complete records of the spraying program are not available, but the order in which the villages were sprayed is as follows up to 9 April. April 1 - Madimutsa, Chimhende, Simende, Teta/Kangira, Chizura. April 2 - Karimazondo, Karonga, Katsamudenga, Katsande, Madja. April 3 - Chakurungama, Ndemera, Kashiri, Mayoshi. April 4 - Kutogora, Nyabote, Machona, Madja, Chadziyamupata. April 5 - Zambezi, Tirivangasi, Nyamukwana. April 6 - Beto, Nyakabawu, Katsande/Gwanza. April 7 - Botsanzira/Kugarahanya, Nyamutanga, Chimusasura. April 8 - Chikurungwe, Muramba. April 9 - Musanhi, Kuparira. It has not been ascertained clearly what criteria was used to spray which villages or in which order, though it is believed that villages furthest away from Kawere Clinic were sprayed first. By the number of clinical cases from each village (Appendix Nine) it can be seen that the worst infected villages were Kugarahanya which was only sprayed on the seventh day, and Kawere Village which still had not been sprayed by Day 9. It should also be noted that some of the villages sprayed never recorded a single case of clinical malaria at the clinic i.e Chimhende, Teta/Kangira, Karimazondo, Karonga, Katsamudenga, Mayoshi, Nyamutanga, Chikurungwe and Muramba. Other villages such as Hunda which recorded fairly reasonable number of clinical cases were not sprayed at all despite lying close to a dam which should always be suspect in any malaria outbreak. Source Reduction From 5 May to 19 May, larval surveys were made of 160 water bodies (134 shallow wells and 26 ponds). Records from Kawere Clinic state that mosquito larvae were found in all but 35 of the water bodies surveyed, but it was not specified whether these were anopheline or culicine. It was also reported that the water bodies were surveyed by eye only, without the use of scoops. The E.H.T of Kawere who took part in these surveys states that none of the staff undertaking the survey would have been able to recognise Anopheles gambiae complex larvae, though were able to distinguish between anopheline and culicine larvae. All the anopheline larvae found on a larval survey on 6 July were not Anopheles gambiae complex, though there were many places seen during this time which would have been favourable for their breeding. As a follow up to the larval survey, 125 ponds in which larvae were found were sprayed with old engine oil, and a further 52 ponds had weeds cleared, though it is not clear if the weeds were removed from within the water bodies or around their edges, though information suggests the latter. Health Education During the malaria outbreak a health educational program was carried at three villages Kugarahanya, Chitiyo and Kawere. A complete copy of the health educational literature was not found but what was seen told people to report to the clinic on the first signs of symptoms and suggested people prevent malaria through the use of prophylactics, repellents, mosquito nets and cutting grass around their houses. The villages in which health education was carried out all lie close to the clinic making it easy for them to report to the clinic. Evaluation Of Control Activities It is impossible to evaluate the effectiveness of the control methods undertaken as no blood slide submissions forms were found to cover the period during and after spraying. Clinically there was a marked reduction in clinical malaria after the various control activities, but it should be noted that in all other clinics investigated, May clinical malaria figures are reduced from those of April (Appendix Eleven) and even in the Kawere area, all villages sprayed or unsprayed shows a decrease in malaria from April to May (Appendix Nine). This is not to say that the control methods were a waste of time, simply there is not enough data to make a good analysis. Table One shows an unusual increase in malaria at Mutoko Hospital from April to May, and perhaps this might have been the pattern at Kawere if no control measures had taken place. Usually though, country wide it is unusual to get an increase in malaria from April to May even in so called 'endemic' areas as surface water and temperatures have both decreased limiting both mosquito and parasite development. Locality Of The Outbreak The exact locality of possible transmission sites is impossible without being able to see blood slide submission forms for the period of the outbreak. Of the 94 villages in the Kawere Catchment Area, 39 recorded at least ten clinical cases of malaria per village, though only eight recorded more that 50 cases (Appendix Nine). Of the eight worst infected villages, three lie at some distance (over one hours walk) from the clinic. The two worst infected areas (clinically), Kawere and Kugarahanya (Appendix Nine) both lie within easy access to the clinic. It would be expected that the positivity rates of the two villages might be much less that other villages some distance away where real effort is needed to come to the clinic. Coupled with this only three villages (Kawere, Chitiyo and Kugarahanya) were given health education, and one of the primary aspects of this education is to encourage people to come to the clinic if they feel ill in any way. This is not to say that these villages did not have a malaria problem, simply that there problem may not have been as bad as it appears clinically. Kugarahanya and Chitiyo were visited. Local people stated that there had indeed been a problem in the area, and say that it was the worst they remember in living history. People also stated that malaria was a permanent feature of the area, but it was felt that the people spoken to had incomplete knowledge of the actual symptoms of malaria as a disease. Much of Kugarahanya and Kawere Villages lie alongside vleis. The vleis appear as though they would be swampy during the wet season, and when seen during the investigation were the site of many shallow wells and ponds along the length of the river beds. Anopheline larvae were found in some of the ponds, but not A. gambiae complex. However, in other parts of Zimbabwe, A.gambiae complex larvae have been found in similar situations (Freeman 1992) suggesting that the ponds may have acted as a breeding site for the vector mosquitoes. The case of Chitiyo and Nyabote is more interesting. Both villages are serviced by a single bore hole which produces sweet water and is used by many people in the area. The borehole is situated in a vlei surrounded by many shallow wells, and local people stated that people visited this site throughout the day and late into the evening suggesting that people in the area may have been catching malaria from possibly a single focal point. Indications from the clinical records do suggest that the transmission sites of the outbreak were widespread, but until slide submission forms are seen and local movement of people analyzed the true focal areas of the outbreak can never be ascertained with any certainty. Climatic Data Temperatures By referring to Appendix Five it becomes evident that if the past decade is compared with the previous decade then average rainfall has decreased by about 150 mm and annual temperatures have increased by about half a degree centigrade. From Appendix Six it can seen that the hottest month on average in Mutoko is November. The increase in temperature is not even across the year. Appendix Six shows temperature changes over the last two decades. While October has become fractionally cooler, August and September have remained almost the same, and all other months have become appreciably hotter (1C) especially the critical winter months of June and July. As winter temperatures determine mosquito distribution, Appendix Seven shows aspects of either June or July (which ever is coldest in a particular year) temperatures. The graphs show mean minimum temperatures, the absolute minimum air temperature recorded for each winter. As with mean July and June temperatures, all these temperatures show an increase in the past decade. Most interesting is that possible malaria outbreaks recorded correspond with warmer winters as noted in the malaria outbreak of Mberengwa (Freeman 1984), though not enough data in Mutoko exists to support the theory here. Besides determining mosquito survival in an area temperatures also determine parasite survival. Appendix Seven shows the mean temperature of May to August of each winter. It can be seen that since 1985, 1987, 1990 and 1992 were all comparatively warm and therefore short winters. 1987 preceded 1988 which has reasonable rains, the same applies to 1992 which preceded 1993: 1990 preceded 1991 which generally had poor rains. The winter of 1993 has also been comparatively warm facilitating both vector and parasite survival. Chloroquine Resistance In Zimbabwe, chloroquine resistance is fairly widespread though as yet not at a high level (Chandiwana et al 1992). It must be assumed that chloroquine resistance may have been a feature during the present outbreak. The clinics of Mutoko District are supplied with Fansidar. Kawere Clinic staff reported treatment failures with chloroquine, but treatment with Fansidar was not correlated with blood slide data so it is impossible to say whether the 'chloroquine resistance' was a case of chloroquine failure or treatment of cases which were not malaria, though it is fair to assume in the circumstances, that some chloroquine resistance was probably around. GENERAL COMMENTS AND OBSERVATIONS Malaria Data The compilation of this report has been made more difficult than necessary due to the lack of good malaria data. Mutoko District cannot be completely blamed for this situation as few health institutions in the country keep adequate records. To make any assessment of malaria in an area, one cannot use clinical data. While clinical data can give some indications of malaria incidence, it is notoriously unreliable as most health institutions in the country over diagnose malaria (Freeman 1993b). Malaria is often focalised (Freeman 1993d) and while clinical data may give the impression of transmission being widespread, knowledge of the actual addresses of malaria cases and age profile can lead to great insights about disease transmission in a particular area. For instance children rarely move far away from home while adults may roam about the whole country. Therefore, if many proven cases of malaria are found in the two to fourteen age group of children, transmission sites are likely to be nearby. Similarly, if whole households suffer from malaria at the same time, it suggests that transmission is occurring at home (unless of course a whole family has travelled to a known malarial area). However, it is often the case that one or possibly two members of a family suffer from the disease at any given time suggesting that transmission is occurring elsewhere. It might be found that only men or women are suffering from the disease, and if the cases are proven, all that is necessary is to look for the common denominator between the cases. Documented cases from Gokwe show that in one case only men were suffering from malaria and investigations showed that they all worked as security guards at one site with a breeding site of vector mosquitoes (Freeman 1992) and in other cases, families who fetch water at night had a much stronger likelihood of catching malaria than those who did not (Freeman 1993d) - the assumption being that they frequented areas of mosquito breeding at night when they fetched water - a similar situation may have occurred at Kawere at Chitiyo and Nyabote villages, The most important records for any investigation are there blood slide submission forms which contain all the information necessary (if filled out correctly) so that any malaria case can be followed up and investigated. The following was observed concerning data collection 1) T5 Forms - Clinical Malaria Most health centres visited were able to produce T5 forms when requested, but rarely were they complete or going back for any great period of time except for Makosa Clinic. The general way in which T5 forms are kept suggests that they are rarely consulted after completion as they are usually thrown into a file in no systematic way. T5 forms at Mutoko Hospital were well ordered for 1991 and 1992 but thereafter were thrown into a loose leaf file in no systematic way and many forms were missing for a number of clinics. At Mutoko Hospital, T5s slated for Mutoko Hospital contained the same figures as T5 forms stating that they were combined district figures for 1993. 2) Blood Slide Submission Forms No health centre in Mutoko was found with a complete record of blood slide submission forms except for Hoyuyu One. Generally when asked for, the staff would spend much time looking for them and would be found in an envelope or box stored in no systematic way. When found, few forms would be present, even though all clinic staff stated that blood slides were taken of all malaria cases. The system of recording blood slides also leaves a lot to be desired. The clinic makes out three forms when taking a blood slide, submits all three forms to the district, and then the district after examination then returns all three copies. One can only wonder why three forms are taken at all in such a system, and since all three forms remain together, it means that when they are lost they are also lost together. The only record of blood slides examined at Mutoko Hospital is that of how many slides were examined for each clinic in each month, and how many were positive. However, it appears that even these records might be misleading as there is evidence to suggest that the records reflect the time when the slides were examined, not when they were actually taken. Appendix Ten shows the records of clinic blood slide submissions and positivity rates for the last two years: slide records for previous years were not available. It can be seen that the submission of blood slides is extremely irregular from all health institutions especially during the winter months. It appears that Kapondoro, Kushinga, Lucky Dip and Nyadire Mission have not submitted a single slides for the whole of 1994 (Appendix Ten). This means that the district staff can never be aware of any problems at these health centres unless warned by the health centres concerned - which is often too late. It appears that Nyadire Mission submits slides directly to Blair Research Laboratory. Staff at Blair Research report that no other centre in Mutoko submits slides to them. Sending slides to Blair Research is a complete waste of time: they are over swamped with slides, and the last slides examined from Nyadire Mission were from December 1993 examined only in June 1994. Worse still, the actual submission forms from Nyadire Mission for this period were never submitted. However, of the 52 slides submitted by Nyadire in December 1993, 23 were positive suggesting that Nyadire already had a potential problem early in the season. But this information comes far too late. It must be concluded that despite clinics claiming to take slides of all suspected malaria patients this is not the case, even though all of them say that they submit slides but rarely get the results returned. Blood Slide Examination Mutoko Hospital has two microscopists. One microscopist should be able to examine 50 slides a day so between two microscopists they should be able to examine up to 2000 slides a month if neither takes leave. If each microscopist takes six weeks leave a year, it should be possible that they can examine 20 000 slides a year which is more than adequate for a district that reports a maximum of 9 000 cases of clinical malaria in a year and instructs their clinics to take slides of all suspected malaria cases. The truth of the matter is that the two microscopists are asked to carry out many other duties and rarely are both microscopists in the laboratory at the same time. Worse still neither appears to know what the other is doing so that when records are kept each has his own particular way of doing things. The microscopist spoken to mentioned that a percentage of slides were sent to Blair Research Laboratory for quality control. Blair staff did not mention that this was the case, but on the other hand they have so many slides lying around it is doubtful they can recall who has submitted what in the last six months. Analysis Of Blood Slide Results Often blood slides are only taken when malaria has been established to be in an area as in the case of this outbreak. The purpose of taking slides does not help in clinical diagnosis as the slides often take weeks to be examined, and the results are used to simply fill in statistical forms which give some idea of the extent in numbers of patients in any given outbreak but little else. When the location of an outbreak is established and is actually taking place, it is only of academic importance whether positivity rates are 25% or 50%. The most important time for taking slides is when the presence of malaria is not known i.e in the case of Mutoko District throughout the year until the presence of malaria is established in any given area after which time it is not so important. The saddest thing about the whole situation countrywide is even when all the above things are done correctly, i.e taking of blood slides, filling forms out correctly, examination, returning to clinics etc, the blood slide examination forms are rarely looked at if at all. This is not only the case in the districts, but also in the provinces and even such institutions as Blair Research Institute and the head office of the Ministry of Health and Child Welfare. A great deal of important information is collected which simply collects dust. However, it was extremely pleasing to note that Mashonaland East Province are doing something to correct this situation by computerising all blood slide submission results, though it is doubtful that they have received much in the way of submissions from Mutoko. Lastly, malaria records should never be thrown away: the history of malaria in any given area can give guidance to present problems. It was disturbing to be told by Nyadire Mission that they destroy records after five years. In the case of the district, if they must send records to archives after five years, clinics should be encouraged to hang onto their records for as long as possible as this is where any investigation is likely to start in the event of a malaria outbreak. Chloroquine And Village Community Workers According to health staff spoken to in Mutoko District, VCWs are issued with chloroquine. The pharmacy at Mutoko Hospital states that chloroquine is still issued directly to VCWs from the hospital while Makosa Clinic stated they had stopped the practice because there was a shortage of chloroquine, and Kawere Clinic staff stated they were not aware of such a policy despite their records showing that they had issued chloroquine in 1990 (Table Three). The whole question of the issuance of chloroquine to VCWs should be carefully looked at. Apart from the risks of increasing chloroquine resistance, if VCWs are in the habit of administering chloroquine and people first seek treatment with them, malaria problems in an area might become hidden because people do not visit clinics. Clinics apart from being treatment centres are also sentinel points in their own right. If people do not report to clinics then they are not aware of problems in their area. Looking at Table Three also raises other questions. If chloroquine usage at Kawere Clinic were taken as a measure of malaria in an area it can be seen that chloroquine usage has not varied by as much as the clinical cases. One must also wonder about the figures. In 1992, records suggest that five tins of chloroquine were used for treatment when only 155 cases of clinical malaria were reported all year. Five tins of chloroquine should be able to treat 500 hundred adults. The same applies in 1993 where 436 clinical cases are reported yet enough chloroquine is used to treat 1100 adults. TABLE THREE KAWERE CLINIC Chloroquine Usage Amount of chloroquine (x1000) issued from Kawere Clinic from May 1989 to June 1994.
An attempt was made to carry out a similar analysis for the whole district but this proved impossible as clinics can order directly from medical stores or from the hospital pharmacy. It is doubtful that Central Stores would be prepared to gather this information from their records as it would require a lot of work. Rainfall Rainfall is particularly erratic in this area as seen from Appendix Five. High rainfall does not mean high malaria as it depends on the pattern of rainfall. However years with good rainfall are likely to be higher risk years for malaria than those with little rain as seen in 1992 during the drought. The worst conditions for malaria are heavy infrequent showers: in these type of conditions, mosquitoes can breed very rapidly, and if the mosquito vectors are not already present they can spread rapidly into the district from outside along river beds such as the Nyadire River. However, when migrating into the area, the season and the peak of the outbreak is likely to be later in the season. Control Methods Used During The Outbreak Residual House Spraying While in the company of Mr Mukandi (E.H.T Kawere) a number of householder were interviewed in the Kugarahanya area. One householder showed a hut infested with German Cockroaches Blatella germanica. This householder claims that his house was sprayed, yet after spraying not a single dead thing was found in the house. It was claimed that other houses in the same vicinity had the same problem. Mr Mukandi was one of the spraying supervisors during the spraying exercise (though not of Kugarahanya) and he expressed great surprise at this discovery as he claims that when spraying under his supervision, householders were particularly happy with the fact that Fendona killed cockroaches and he himself had witnessed this to be in the case of all the houses he had followed up on. Fendona is a very powerful insecticide which kills all insects: it can only be assumed that the houses in Kugarahanya investigated had not been sprayed properly. The validity of residual house spraying so late in a season must also be questioned. It is expensive in terms of insecticide and man power. Expense appeared to be an issue, because when asked why oil had been used instead of larvicides, all people questioned stated it was a matter of a lack of finance. One bottle of Fendona which sprays about eighteen houses would have cost the same price as a bottle of larvicide which would have sprayed all the wells in the area (probably several times over). Source Reduction Source reduction can be a very powerful tool to reduce malaria in certain situations. Kawere appears to be one of those areas where it is applicable as water bodies are restricted along stream beds which are easily accessible. The choice of using used engine oils and cutting grass around wells must be questioned. Used engine oil is extremely dirty and often renders water unusable afterwards: it caused consumer resistance to control strategies which occurred at Kawere, and many householders only allowed its use after a lot of persuasion. Worse still, used engine oil is often not as effective as it should be as it often collects to one side of the water body leaving gaps where larvae can survive. Larvicides are a much better option where chemicals must be used. Readily available in Zimbabwe is Coopex (permethrin) which is very cheap and effective. It is completely safe to people and live stock. It will kill fish if used incorrectly, though fish and larvae are rarely found in the same place! One bottle of permethrin costs about $70 and can spray up to two hectares of water which is an extremely large amount of water. Shallow wells seen in Kawere were rarely greater than ten square metres, and therefore one bottle would be able to treat 1000 wells of such size. The other possible advantage of permethrin is that it tends to collect at the surface of water. Indications from a malaria outbreak in Gokwe suggested that malaria cases in an area treated with larvicide disappeared much faster than expected and it was concluded that the female vector mosquitoes were being killed as they tried to lay eggs (Freeman 1992). Without this property, source reduction would normally take six weeks before a reduction is malaria is noted, because it only deals with larvae and not adults. Adults can live for up to a month, and therefore even if every larvae were killed the adults would still be expected to transmit malaria for up to another four weeks: the last infected people would get sick two weeks later giving a total of six weeks. It is for this reason that house spraying is usually favoured because it acts on the adults immediately, and two weeks later a reduction of malaria cases should be noted. If weeds are going to be dealt with in ponds, it should be the weeds inside the pond rather than those around the pond. However, it should be noted that certain weeds discourage mosquito survival while other thick weeds such as Spirogyra aid mosquito survival by giving them protection from predators (Freeman 1992). Lastly it should be noted that environmental methods of control should always be preferred to chemical solutions, and ponds with no problems should be left alone. In this respect, health staff who are asked to do larval surveys should have been provided with soup spoons (scoops) so that they could dip into water. Trying to see larvae, let alone identify them by eye while in ponds is extremely difficult! Other Clinics All the clinics visited except for Hoyuyu One lie in areas in which malaria should be expected. Why Kawere has had so little malaria in recent years must remain a mystery. However, a bigger mystery is that of Hoyuyu One which lies in one of the highest parts of the district and therefore one of the places least likely to have malaria. The area lies on the divide of the water shed of both the Nyadire and Inyansizi Rivers, and if malaria transmission is actually taking place around Hoyuyu One then mosquitoes are likely to migrate through either one of these river systems. If this is the case, the question is where is the starting point for this migration i.e the winter survival limits. Evidence from Gokwe suggests that mosquitoes may survive up to 1000 metres in altitude, but if this is the case in Mutoko why is malaria so scarce in such areas such as Kawere which lie below this altitude. If the vector is indeed able to survive at these altitudes, then the Manemba Dam near to Nyadire Mission needs to be investigated. This dam lies at 1000 metres, and if mosquito vectors are surviving over winter in this dam, then it would be expected that positive malaria cases should appear from September onwards in villagers living around the dam. Nyadire Mission should easily be able to pick up such cases if they take blood slides during this period. Other dams should also be considered suspect. Both Kawere and Makosa have dams in their catchment areas. A number of positive cases from Makosa were recorded around the Makosa Dam and when surveyed, the dam had many microhabitats suitable for A. arabiensis survival, though only other species of anophelines were found at the time of survey. CONCLUSIONS Few conclusions can be drawn up with the data available, but the following inferences might be made. 1) The winter rise of temperatures over the last decade should favour the survival of malaria in Mutoko District if the old limits of 900 m for vector survival apply. 2) The malaria situation in Mutoko is only likely to get worse rather than better, though it is doubtful that malaria will become a seasonal problem for much of the district in the near future. Increased and improved surveillance is needed if the epidemiology of the area is ever going to be understood and appropriate control measures enacted. 3) There is still not enough evidence to justify any large scale expensive malaria control measures in the district such as house spraying at present, though cheaper options such as health education could be considered. The best approach is that of improved surveillance so that impending problems may be dealt with quickly. RECOMMENDATIONS Blood Slides 1. The control of malaria primarily involves good information. It is recommended that EITHER If the district is truly capable of taking blood slides from all clinical cases of malaria then it should do so and this should be enforced. OR If resources are limited and the district is unable to examine all slides from all patients then it is recommended that blood slides be taken from all suspected malaria patients from all clinics in the area below 1200 metres from August onwards each year until such time that malaria is established in any given locality. If malaria is established in any given village, a blood slide from one out of every five or even ten patients from that village would suffice. This should not be very difficult to do, as the number of clinical malaria cases even in endemic areas is very small from August to December. If no outbreak occurs, then numbers of slides will remain very small. The least important time for taking slides (if a rest is needed) is from May to July if no malaria is established in an area. 2. Along with the taking of slides it is most important that blood slide submission forms are completed correctly especially the village or "sabhuku" of residence of the patient (not the address of the health institution). 3. All blood slides taken should be submitted to the district hospital only - not to Blair Research Laboratory. 4. Three copies of the blood slide submission form need to be made, one to remain at the clinic and the other two sent to the microscopist examining the slide. After a slide is examined, one copy of the completed form should be filed at district (in a single file separated into different clinics), and the other copy should be returned to the clinic submitting the form who can then throw away the fist copy and file the second completed copy at the clinic where it can be a permanent record. 5. When a clinic receives their returned blood slide it should first be examined before filing. If it is established early in the season (i.e when numbers are few) that someone is positive for malaria, they should be followed up and counselled. Even if indications are that the case is imported, it is important to stress to the affected person that they may now be a carrier of malaria and may infect the rest of the population. Health education should stress the necessity of avoiding mosquito bites so that they do not infect local mosquitoes and hence other people in the area. If the above recommendations take place it should also improve the diagnostic skills of clinic staff so that fewer and fewer slides are actually submitted. 6. Emphasis needs also to be placed on the keeping of T5 forms, as positivity rates combined with clinical cases of malaria give a much clearer pattern of malaria in any given area than either record on its own. 7. With the above recommendations it is also recommended that a percentage of all slide examined by any given microscopist be re-examined by other microscopists to ensure that microscopists retain their expertise. There are many cases around the country where microscopist diagnosis has proved to be faulty. District microscopists should be examined by provincial microscopists who in turn should be examined by Blair Research Laboratory. It should also be noted that the microscopists at Mutoko Hospital need a set routine if they are to carry out their duties properly. If as stated they are continually asked to carry out other duties, their performance as microscopists will never be as good as it can be. 8. Another monitoring activity which has often been discussed is that of doing prevalence surveys. However, in marginal areas such as Mutoko this activity is likely to lead to inconclusive results. The most useful time to carry out a prevalence survey is prior to a malaria season to assess transmission potential. However, the chances of finding the few individuals (if any) who are harbouring parasites is very remote by this method, and it is easier and better to have passive surveillance of people turning up at clinics sick. Control Strategies As Mutoko District is a marginal malarial area, intensive control programmes such as residual house spraying are unlikely to be cost effective. There is no justification at present for residual house spraying to be carried out in Mutoko District prior to a malaria season until the epidemiology of the area is better understood. Control is better carried out when a problem is identified, but to be fully effective, the problem should be identified early by the surveillance methods described above. If it is established that malaria is present in any given area then the following strategies might be considered after a thorough investigation of all the factors of an outbreak, mainly the exact locality of the transmission. 1. Residual House Spraying House spraying can be very effective if done correctly and seems applicable to many areas in Mutoko in response to a known outbreak. However, to be cost effective a number of factors have to be taken into consideration. a) March is usually the peak transmission month and thereafter transmission declines. Residual house spraying after March is usually not cost effective. b) If households are close together and close to breeding sites as in the case of Kugarahanya then house spraying can be a very good option. If houses are a distance from breeding sites, i.e when rainfall has finished, transmission is unlikely to occur at houses and therefore is likely to be ineffective. c) If rainfall is still imminent allowing breeding sites to be established in numerous places then residual insecticides must be considered. It can never be said that house spraying as being a waste of time, simply there might be better cost effective options. Often though, house spraying is carried out as a community service so that the effected communities feel that the health services are actually doing something useful! 2. Source Reduction This includes both environmental control and larviciding, but in this section larviciding will be discussed and environmental control under health education. If personal observations from Gokwe and this particular outbreak are correct, then malaria transmission in these situations is extremely focalised. If the focal points of transmission can be identified then larviciding can become a very powerful tool and if malaria is identified in any given village it requires little knowledge to identify probable potent areas of possible transmission. Since most water in Mutoko is in wells and the occasional dam, then it must be considered that the places of greatest potential for mosquito survival must also be along the vleis where the wells and dams are found. Two strategies of larviciding can be considered. The first is using larvicides to destroy mosquitoes during the winter. In favour of this approach is that during the winter mosquito breeding is extremely limited, and development of the larvae may take as long as two months requiring very infrequent spraying. However, this approach at present is not applicable to Mutoko until the approximate limits of mosquito vector survival can be established. While it is possible to carry out random samples of wells and dams in the district, it is better and easier to collect blood slides during August to December and spot where possible malaria cases are coming from and hence early transmission. The following winter these areas can then be surveyed and if larvae found then destroyed. The other larviciding strategy is to spray during the malarial season around potential trouble spots. However, during the summer mosquito breeding can be completed within a week and therefore for larviciding to be useful it must also be carried out weekly, which while being still very cheap in insecticide, is very time consuming and consequently expensive if health staff are used. However, one strategy which is being utilised in Gokwe is to involve responsible members of the community. If local people can be trained in larval recognition and spraying, then larviciding can be carried out with little cost to the Ministry of Health and Child Welfare. In reality, if someone is properly trained, most cases of larval breeding can be dealt with just as quickly and more permanently by environmental methods. 3. Health Education As social factors may have played a part in this malaria outbreak, health education could have one of the most powerful effects on further outbreaks. The main points that health education should cover are: Changes In Social Behaviour People should be aware of the general transmission characteristics of the disease especially the relationship of vector breeding and peoples activities. Points to stress are Seeking early treatment when ill during the malarial season. Keeping away from potential transmission sites at night. In the case of the Mutoko District not fetching water at night and if possible not walking along river beds after dark. Where dams occur avoiding the edges of dams after dark. Places to avoid in particular are places of great human and animal activities i.e gardens, brick making, water fetching points used by many people and places where cattle drink. Preventative Measures If breeding sites must be visited then precautions should be taken including, taking prophylactics and repellents (it was pleasing to note that Mosbar was on sale in shops in Mutoko at reasonable prices). For prevention of transmission in houses, repellents and mosquito nets for those who can afford them. While mosquito coils might be considered, they only work in houses and irritant to people breathing in the smoke. The slashing grass around houses (often promoted by the Ministry of Health) is considered an almost complete waste of time and energy unless the slashing is carried out for a large distance from peoples homes. The same applies with wearing clothing that covers the whole body: generally malarial areas are very hot, and it is difficult to persuade people to wear socks, long trousers and long sleeve shirts with only the hands and face exposed which still require treatment with repellents. However, it is my personally felt that of all the methods described above, the most potent is that of keeping away from water bodies at night. While health education is normally directed at the population as a whole, indications from Gokwe suggest that health education may be particularly powerful if directed at people suffering from malaria i.e future potential carriers. In this case health education is directed at stopping people infecting mosquitoes rather than mosquitoes infecting people. Vector mosquitoes only transmit malaria if they bite an infected person: if people with malaria stay away from mosquitoes, transmission stops (Freeman 1993d). During heavy rains when small pools are created everywhere, environmental methods of reducing mosquito breeding sites should discussed as part of health education. Ironically in other parts of Zimbabwe, many households dig rubbish pits after health education which then become good mosquito breeding grounds (Freeman 1993d). As for the people who actually live near water bodies they must be encouraged to take prophylactics and use mosquito nets and repellents. It should be noted that there can be one effect of taking prophylactics such as Malasone and Deltaprim as recommended in this country. Work from the Gambia has suggested that this prophylactic stops people getting ill, but does not completely stop the parasite developing in the human host. The result of this can be that the person becomes an inadvertent carrier (Greenwood et al 1988). While this is very good for the people exposed to malaria all the time, it does mean that the parasite remains hidden in the population unless a prevalence survey takes place. It was interesting that no prophylactic failures were reported in Mberengwa where the main control strategy used during the malaria outbreak around the Manyuchi Dam was the distribution of prophylactics, but it would be interesting to see if any malaria cases appear after people stop taking their prophylactics during the winter. 4) Chloroquine Distribution It is recommended that if chloroquine is distributed to Village Community Workers, that this is only done once an outbreak of malaria has been identified, and then the chloroquine given only to VCWs of affected villages. Once the outbreak is finished, it would be better that the chloroquine is removed from the VCWs. 5) In Conclusion Being forewarned about problems is a much better control strategy than blanket spraying of houses or any other large scale control activity. REFERENCES Bruce-Chwatt, L J. (1985). Essential Malariology - 2nd Ed. William Heinemann Books Ltd. London. Chandiwana, S.K., Freeman, T.W., Masendu, H.R. (1992). Overview Of Malaria And Malaria Control In Zimbabwe. Blair Research Institute. Unpublished. Crees, M.J., Mhlanga, T.H. (1985). Malaria Prevalence In Zimbabwe and Parasite Survey Of 1983. Zimbabwe Science News. 19:114-117. De Meillon, B. (1934). Observations on Anopheles funestus and Anopheles gambiae in the Transvaal. Publication Of The South African Institute Of Medical Research. 6:195. Freeman, T.W. (1992). Final Report - Malaria, Integrated Control, Ignorance and Community Control. Blair Research Institute. Unpublished. Freeman, T.W. (1993a). Relationship Between Malaria Cases, Temperature and Rainfall - A Case Study From Sassame Mission, Gokwe, Zimbabwe. Blair Research Institute. Unpublished. Freeman, T.W. (1993b). The Over Reporting Of Clinical Cases Of Malaria In Zimbabwe. Blair Research Institute. Unpublished. Freeman, T.W. (1993c). The 1991 National Malaria Prevalence Survey. Blair Research Institute. Unpublished. Freeman, T.W. (1993d). Final Report - Evaluation Of Community Acceptance Of Various Malaria Control Methods. Blair Research Institute. Unpublished. Gillies, M.T., De Meillon, B. (1968). The Anophelinae of africa south of the Sahara. The South African Institute For Medical Research. Greenwood, B.M., Greenwood, A.M., Bradley, A.K., Snow, R.W., Byass, P., Hayes, R.J., N'Jie, A.B.H. (1988). Comparison of two strategies for control of malaria within a primary health care programme in the Gambia. The Lancet, May 21, 1988.(1121-1126). Leeson, H.S. (1931). Anopheline mosquitoes of Southern Rhodesia. Mem. London Sch. Hyg. Trop. Med., no 4: 1. Le Sueur, D. (1994). Aspects Of Survival Of Anopheles arabiensis. PhD Thesis - Still In Publication. Medical Research Institute, Durban, South Africa. Moshkovsky, Sh.D., Rashina, M.G. (1951). The Relationship Of Temperature To Sporozoite Development. Epidemiology And Medical Parasitology For Entomologists. Medgiz. Moscow. (In Russian. Taylor, P., Mutambu, S.L. (1986). A review of the malaria situation in Zimbabwe with special reference to the period 11972 1981. Transactions of the Royal Society of Tropical Medicine & Hygiene. 80(1):12 9. PEOPLE CONSULTED Provincial Medical Directorate Dr M.Nsungu - M.O.H Mr M.Jonga - P.E.H.O Matoko District Hospital Dr Mudzingwa - D.M.O Mr G.T.Mangwadu - Pr.E.H.O Mr E.Mupfururi - Pr.E.H.T Mr P.Mukota - Laboratory Chief Mr S.Jumbi - Microscopist Mrs Chipunza - Health Information Officer Mrs Mazarura - Librarian Mr K.Mudambo - Pharmacy Technician
Mr C.Mukandi - E.H.T Mrs R.C.Bakai - Nurse
Mrs Tsitsi Chipindu - Temperature Section Mrs M.Mbasha - Water section Mrs A.Martin - Head Of Water Section Miss W.Marume - Forecasting Section
Avondale West Harare Zimbabwe
E.Mail - freeman@healthnet.zw |