Changing distribution and abundance of the malaria vector Anopheles merus in Mpumalanga Province, South Africa

Background: The malaria vector Anopheles merus occurs in the Mpumalanga Province of South Africa. As its contribution to malaria transmission in South Africa has yet to be ascertained, an intensification of surveillance is necessary to provide baseline information on this species. The aim of this study was therefore to map An. merus breeding sites in the Ehlanzeni District of Mpumalanga Province and to assess qualitative trends in the distribution and relative abundance of this species over a 9-year period. Methods: The study was carried out during the period 2005-2014 in the four high-risk municipalities of Ehlanzeni District. Fifty-two breeding sites were chosen from all water bodies that produced anopheline mosquitoes. The study data were extracted from historical entomological records that are captured monthly. Results: Of the 15 058 Anopheles mosquitoes collected, 64% were An. merus. The abundance and distribution of An. merus increased throughout the four municipalities in Ehlanzeni District during the study period. Conclusion: The expanded distribution and increased abundance of An. merus in the Ehlanzeni District may contribute significantly to locally acquired malaria in Mpumalanga Province, likely necessitating the incorporation of additional vector control methods specifically directed against populations of this species.

Therapeutic efficacy of sulfadoxine-pyrimethamine for Plasmodium falciparum malaria

OBJECTIVES

To assess the therapeutic efficacy of sulfadoxinepyrimethamine (SP) after 5 years of use as first-line treatment of uncomplicated Plasmodium falciparum malaria, and thus guide the selection of artemisinin-based combination therapy in Mpumalanga, South Africa.

DESIGN

An open-label, in vivo therapeutic efficacy study of patients with uncomplicated P. falciparum malaria treated with a single oral dose of SP, with response to treatment monitored clinically and parasitologically on days 1, 2, 3, 7, 14, 21, 28 and 42.

SETTING

Mangweni and Naas public health care clinics, Tonga district in rural Mpumalanga. SUBJECTS, OUTCOME MEASURES AND RESULTS: Of 152 patients recruited sequentially, 149 (98%) were successfully followed up for 42 days. One hundred and thirty-four patients (90%) demonstrated adequate clinical and parasitological response. Of the 15 patients (10%) who failed treatment, 2 (1.3%) had an early treatment failure, and polymerase chain reaction confirmed recrudescent infection in all 13 patients (8.7%) who had late parasitological (N = 11) or clinical (N = 2) failure. Gametocyte carriage was prevalent following SP treatment (84/152) and this has increased significantly since implementation in 1998 (relative risk 2.77 (confidence interval 1.65 - 4.66); p = 0.00004).

CONCLUSION

Asexual P. falciparum parasites in Mpumalanga remain sensitive to SP, with no significant difference between the baseline cure rate (94.5%) at introduction in 1998, and the present 90% cure rate (p = 0.14). However, since gametocyte carriage has increased significantly we recommend that SP be combined with artesunate in Mpumalanga to reduce gametocyte carriage and thus decrease malaria transmission and potentially delay antimalarial resistance.

Therapeutic efficacy of sulfadoxine-pyrimethamine in uncomplicated Plasmodium falciparum malaria 3 years after introduction in Mpumalanga

OBJECTIVES

To assess therapeutic efficacy of sulfadoxine-pyrimethamine (SP) in treatment of uncomplicated Plasmodium falciparum malaria 3 years after introduction in Mpumalanga, South Africa.

SETTING

Tonga district with a population of 116,418 and subject to seasonal malaria, with an average annual incidence of 3,200 cases.

SUBJECTS

One hundred and nineteen malaria patients presenting to a sentinel surveillance clinic and recruited according to World Health Organisation (WHO) criteria.

METHODOLOGY

Patients satisfying WHO inclusion criteria were treated with a single oral dose of SP and the response of infection to treatment in each patient was routinely monitored clinically and parasitologically on days 1, 2, 3, 7, 14, 21, 28 and 42 post-treatment. One hundred and ten patients completed follow-up to day 42 or evidence of clinical or parasitological failure.

RESULTS

The cure rate at day 42 was 93.6% (103/110). Two patients (1.8%, RII) were early treatment failures on day 3, while recrudescence (4.5%, RI) occurred in 5 patients on day 28 (N = 3) and on day 42 (N = 2).

CONCLUSION

In Mpumalanga P. falciparum remains sensitive to SP, with no significant difference between the baseline cure rate (94.5%) and the cure rate in the present study (93.6%).

Repellent effects on Anopheles arabiensis biting humans in Kruger Park, South Africa

Distribution of biting sites on the human body by the malaria vector Anopheles arabiensis Patton (Diptera: Culicidae) was investigated near a source of mosquitoes in the Kruger National Park, South Africa. Eight adult male volunteers (2 teams x 2 pairs of subjects) conducted human bait collections while seated on camp chairs in the open-air, wearing only short trousers (no shirt, socks or shoes). Mosquito collections during 18.30-22.30 hours on five consecutive nights in April 1998 yielded a total of 679 An. arabiensis females biting subjects with or without their ankles and feet treated with deet insect repellent (15% diethyl-3-methylbenzamide, Tabard lotion). On subjects whose feet and ankles were smeared with repellent, 160 An. arabiensis females were captured biting in 60 manhours: 88.1% on the legs, 1.4% on the arms and 1.2% on other parts of the body, but none on the repellent-treated feet or ankles. On subjects without repellent treatment, 519 An. arabiensis were caught biting in 60 man-hours: 81.1% on feet and ankles, 16.4% on legs, 1.4% on arms and 1.2% on the rest of the body. For individual subjects, the reduction of An. arabiensis bites ranged from 36.4 to 78.2% (mean protection 69.2%). Results of this study confirm previous findings that, in this part of South Africa - inhabited only by wildlife - when people sit outside during the evening An. arabiensis prefers to bite their lower limbs: 97.5% below the knees. Overall, the number of bites by the malaria vector An. arabiensis was reduced more than three-fold (from 26 to 8/person/evening), simply by treating ankles and feet with a consumer brand of deet repellent. Whether or not this provides a satisfactory degree of protection against malaria risk would depend on the malaria sporozoite rate in the malaria vector population.

False detection of Plasmodium falciparum sporozoites in Anopheles marshallii group mosquitoes

A study was conducted to determine the role of members of the Anopheles funestus group in malaria transmission in the Mpumalanga Province, in the northeastern region of South Africa. Female anopheline mosquitoes were collected between January 1996 and November 1997 by means of human landing catches and tested for salivary gland Plasmodium falciparum infections by means of the enzyme-linked immunosorbent assay (ELISA) method with PF2A10 antibodies. Infection rates from April and May 1997 collections were 3.73% and 19.4%, respectively. None of the nonimmune collectors became infected with malaria. The ELISA-positive mosquitoes were tested with a polymerase chain reaction (PCR) malaria detection assay based on sequence variation present in the small subunit ribosomal RNA gene. Only 1.09% of ELISA-positive mosquitoes were PCR-positive for malaria. Initially, all mosquitoes were assumed to belong to the An. funestus group but subsequent molecular taxonomy showed this assumption to be false. The use of a single-strand conformation polymorphism (SSCP) assay revealed only 1 member of the An. funestus group, An. rivulorum. All other specimens produced banding patterns not seen before. Those samples were identified morphologically as An. demeilloni and An. marshallii s.l. These 2 species are not recognized malaria vectors and thus it is possible that the ELISA results are misleading.

Effectiveness of short-course quinine and single-dose sulfadoxine-pyrimethamine in the treatment of Plasmodium falciparum malaria in Mpumalanga Province, South Africa

INTRODUCTION

Quinine therapy for 7 days remains the mainstay for treating hospitalised malaria cases in South Africa. However, limited resources, including available beds and staff, often result in early discharge of non-severe cases, with quinine tablets for outpatient use. The effectiveness of shorter course quinine therapy coupled with a long-acting antimalarial drug has never been established in Africa, in particular in a population without malaria immunity.

METHODS

A study was conducted to evaluate the effectiveness of a 3-day course of therapy with quinine sulphate (10 mg/kg 8-hourly) followed by a single dose of sulfadoxine-pyrimethamine (SP) according to weight category, before discharge, for 133 hospitalised patients with uncomplicated Plasmodium falciparum malaria at Shongwe Hospital, Mpumalanga province, between February and July 1998. Study endpoints included clinical recovery and parasitological cure, including polymerase chain reaction (PCR) 42 days after initiating treatment.

RESULTS

One hundred and thirty of 131 patients (99%) successfully followed up for 42 days demonstrated clinical and parasitological cure. The remaining patient, who had evidence of a recrudescent infection on PCR, was 1 of 61 patients who were still parasitaemic on discharge from hospital.

CONCLUSION

The abbreviated course of quinine therapy coupled with a single dose of SP for the treatment of non-severe hospitalised cases of P. falciparum malaria, in an area with demonstrated low levels of SP resistance, was highly effective. This approach has potential benefits, including reduced duration of hospitalisation, fewer quinine-associated adverse events and protection against the evolution of quinine resistance by limiting unsupervised quinine therapy in the community. It may, however, be prudent to document a negative blood film before discharge from hospital.

Rapid immunochromatographic diagnosis and Rolling Back Malaria--experiences from an African control program

Malaria is a re-emerging disease in much of Africa. In response, the World Health Organization launched the Roll Back Malaria (RBM) initiative. One of six key principles adopted is the early detection of malaria cases. However, the importance of definitive diagnosis and potential value of field deployment of rapid malaria tests in RBM has been largely ignored. The Lowveld Region of Mpumalanga Province, South Africa, is home to a predominantly non-immune population, of approximately 850000 inhabitants, who are at risk of seasonal Plasmodium falciparum malaria. Malaria treatment in this area is usually only initiated on detection of malaria parasites in the peripheral bloodstream, as many other rickettsial and viral febrile illness mimic malaria. The malaria control programme traditionally relied on light microscopy of Giemsa-stained thick blood films for malaria diagnosis. This review summarizes operational research findings that led to the introduction of rapid malaria card tests for primary diagnosis of malaria throughout the Mpumalanga malaria area. Subsequent operational research and extensive experience over a four-year period since introducing the ICT Malaria Pf test appears to confirm the local appropriateness of this diagnostic modality. A laboratory is not required and clinic staff are empowered to make a prompt definitive diagnosis, limiting delays in initiating correct therapy. The simple, accurate and rapid non-microscopic means now available for diagnosing malaria could play an important role in Rolling Back Malaria in selected areas.

Efficacy of three insect repellents against the malaria vector Anopheles arabiensis

Three commercial repellents marketed in South Africa: Bio-Skincare (BSC, oils of coconut, jojoba, rapeseed and vitamin E), Mosiguard towelletes with 0.574 g quwenling (p-menthane-3,8-diol, PMD) and the standard deet (15% diethyl-3-methylbenzamide, Tabard lotion), were compared against a laboratory colony of the mosquito Anopheles arabiensis Patton (Diptera: Culicidae), the predominant malaria vector in South Africa. Human forearms were treated with 1.2 g BSC, 0.8 g PMD towelette or 0.5 g deet and exposed to 200 hungry An. arabiensis females for 1 min, at intervals of 1-6 h post-treatment. Tests were conducted by three adult male volunteers (aged 30-45 years, crossover controlled test design for 3 consecutive days), using their left arm for treatment and right arm for untreated control. Biting rates averaged 39-52 bites/min on untreated arms. All three repellents provided complete protection against An. arabiensis for up to 3-4 h post-application; deet and PMD gave 90-100% protection up to 5-6h, but BSC declined to only 52% protection 6h post-treatment. These results are interpreted to show that all three repellent products give satisfactory levels of personal protection against An. arabiensis for 4-5 h, justifying further evaluation in the field.

Local plants as repellents against Anopheles arabiensis, in Mpumalanga Province, South Africa

OBJECTIVE

To assess the repellency effect of three local plants; fever tea (Lippia javanica), rose geranium (Pelargonium reniforme) and lemon grass (Cymbopogon excavatus) against laboratory reared Anopheles arabiensis mosquitoes.

DESIGN

A laboratory experimental study.

SETTING

Mpumalanga Province, South Africa.

SUBJECTS

Three adult male volunteers.

MAIN OUTCOME MEASURES

Affordable alternatives to synthetic repellents against biting of Anopheles arabiensis mosquitoes.

RESULTS

All three alcohol plant extracts provided significantly more protection (p = 0.012) than alcohol control. The alcohol plant extract of L. javanica provided 76.7% protection against An. arabiensis after a four hour period, and C. excavatus and P. reniforme provided 66.7% and 63.3% protection for three hours, respectively. At five hours post application only L. javanica alcohol extract provided appreciable protection (59.3%) against An. arabiensis.

CONCLUSION

The results of this study indicate that L. javanica, P. reniforme and C. excavatus protect against An. arabiensis mosquito bites with the repellent effect of L. javanica lasting significantly longer than that of the other two plants.

Community knowledge and perceptions about malaria and practices influencing malaria control in Mpumalanga Province, South Africa

OBJECTIVE

To assess community knowledge and perceptions about malaria and its control in a rural setting.

DESIGN

Descriptive cross-sectional survey.

SETTING

Tonga district with a population of 116,418, seasonal malaria with an annual incidence of 3,200 cases.

SUBJECTS

Female heads of 299 randomly selected households.

METHODOLOGY

A total of 299 households were selected from a random sample of 30 clusters. Community knowledge and perceptions about malaria and its control were assessed by interviews with the female head of each of the 299 selected households.

RESULTS

Respondents ranked malaria as the third most serious health problem facing the community after TB and AIDS. Seventy-two per cent (214/299) of respondents reported that they knew what malaria disease was and of these, 92.1% (197/214) mentioned mosquito bites as the cause of malaria. The respondents' understanding of the causal role of mosquitoes in malaria was significantly related to their knowledge about disease symptoms (P < 0.001). Reported community compliance with the malaria control programme (MCP) was satisfactory; 86.6% (259/299) of respondents reported that their homes had been sprayed during the past 2 years but 10.0% (30/299) did not know why homes were sprayed. Hospitals or clinics were the facilities where respondents most commonly sought treatment for fever; 66.9% (200/299) reported that they would seek treatment immediately after the onset of high fever. Specific practices such as replastering or washing of inside walls compromised the effectiveness of the MCP. Personal preventive measures were sometimes used against malaria (50.8%, 152/299) and use was positively associated with education level (P = 0.001). Respondents expressed their desire for more information about malaria and their willingness to contribute to the control of malaria in their community.

CONCLUSION

The survey collected information which was directly relevant to the development of health education messages to increase community awareness of the problem of malaria, to emphasise the importance of early diagnosis and prompt treatment of malaria, to improve community understanding of the function of indoor residual spraying, and to enlighten the population of the role of mosquitoes in malaria transmission and the availability and benefits of personal protection measures against mosquito bites.

A field trial of microencapsulated deltamethrin, a synthetic pyrethroid, for malaria control

The synthetic pyrethroid deltamethrin was evaluated as a 15 mg/m2 residual application of a microencapsulated formulation for efficacy in malaria control in a 50 km2 area of north-eastern Zimbabwe. Results were compared with very large contiguous DDT sprayed (2g/m2) and unsprayed areas. A total of 3544 rooms were sprayed with deltamethrin. No significant side effects of the insecticide on spraymen were noted. Mosquito captures were poor and inconclusive due to drought conditions, but the malaria vectors Anopheles arabiensis and An. gambiae were identified in the area, the former being 14 times more abundant than the latter in bait collections from an unsprayed area. Monthly bioassays using laboratory-reared An. arabiensis showed a higher mortality of mosquitoes exposed on roofs for up to eight months after deltamethrin application and indicated a high mortality in deltamethrin sprayed houses than in DDT sprayed houses. Tests indicated that, after eight months, up to 50% of the deltamethrin remained on the roof and 25% on the wall. Malaria transmission, evaluated by blood slide surveys at the beginning and end of the transmission season, was high in the unsprayed area, slightly less in the adjacent and incompletely isolated deltamethrin sprayed area, and absent or very low in the DDT sprayed area. The results were considered to be favourable for the use of deltamethrin in malaria control by means of residual house-spraying with the non-irritant dosage of 15 mg/m2, but require evaluation in larger trials.