Joan H. Bryan

Studies on the transmission and prevalence of Bancroftian filariasis in four coastal villages of Tanzania

In surveys of Bancroftian filariasis in four coastal villages in Tanzania, microfilaria rates varied between 28·3 and 15·6% and hydrocoele rates in males over 20 years between 78–5 and 61–3%.Quantitative studies on the intensity of transmission were conducted over a period of 17 months. The estimated potential infective bites per person per year varied from 24 to 189. The number of infective bites was related to filarial endemicity.The vectors in order of importance were Anopheles gambiae s.l., Culex pipiens quinquefasciatus and An. funestus. In all villages An. gambiae s.l. played a role in transmission and in two it was the main vector. Of the total estimated bites by members of the gambiae complex, 16 223 (91·1%) occurred during or following the ‘long rains’ (April to early June). In contrast, transmission by C. p. quinquefasciatus occurred throughout the year. In one village in which C. p. quinquefasciatus was the predominant vector, the biting density of this species was 22 times greater than the bit...

Studies on the sibling species Anopheles gambiae Giles and Anopheles arabiensis Patton (Diptera: Culicidae) in the Kisumu area, Kenya.

A study was undertaken of the seasonal abundance, feeding habits, resting habits and malaria infection rates of the sibling species Anopheles gambiae Giles and A. arabiensis Patton on the Kano Plain, Kenya, and the surrounding foothills. A. arabiensis was the dominant species on the plains and A. gambiae in the foothills. A. gambiae was highly anthropophilic with 92% feeding on man, whereas 59% of A. arabiensis fed on cattle. In both species, the choice of host was affected by the availability of cattle. A. arabiensis rested out of doors more commonly than A. gambiae . The sporozoite rate in A. gambiae was 5·33%, 15·98 times higher than the rate of 0·33% found in A. arabiensis .

Malaria control in Central Malaita, Solomon Islands: 1. The use of insecticide-impregnated bed nets

The present study investigated the use of insecticide-impregnated bed nets by communities in central Malaita, Solomon Islands. Qualitative and quantitative data were collected by: (1) questionnaire administration to 124 care-givers of children aged 0-10 years of age; (2) 20 focus group discussions; (3) two structured observations of bed net re-impregnation, and (4) interviews with key informants. Ninety-four percent of all care-givers had bed nets, but only 62% had sufficient bed nets for all household members. Fifty-two percent used bed nets throughout the year and 70% of care-givers reported that all their children slept under bed nets. Although coastal householders considered malaria and mosquitoes more of a problem than inland householders, overall bed net compliance did not differ. Factors affecting bed net ownership were cost and community expectation of free bed nets. Bed net use was affected by four factors: (1) seasonality (99% used bed nets during the rainy season, 52% used them all year); (2) mosquito nuisance (59% of respondents reported that protection against mosquitoes was the main reason for using a bed net); (3) weather (68% of care-givers would not use a bed net if the weather was hot), and (4) low density of mosquitoes (respondents who used bed nets as protection against mosquito nuisance were more likely not to use bed nets when mosquitoes were few than those who used bed nets for malaria protection (odds ratio (OR), 3.9; 95% confidence interval (CI), 1.4-12.0). Protection against malaria was the main reason children slept under bed nets. Children from households where bed nets were used for malaria protection were more likely to sleep under bed nets than children from households where nets were used as protection from mosquitoes only (OR, 2.7; 95% CI, 1.3-5.9). Other factors that affected childrens bed net use were, age (users were significantly younger than non-users; chi(2)=7.9, degrees of freedom=1, P=0.005) and sufficiency of bed nets (OR, 2.0; 95% CI, 1. 3-7.0).

Effectiveness of dengue control practices in household water containers in Northeast Thailand.

Objective  To investigate the influence of larval control methods (using temephos, keeping fish and covering containers with lids), water use and weekly cleaning of containers on the presence of Aedes aegypti larvae in water‐storage containers in rural and urban households in Khon Kaen province.

The potential of ivermectin to control the malaria vector Anopheles farauti.

We investigated mortality in Anopheles farauti mosquitoes, a major coastal malaria vector in the south-west Pacific, fed on a volunteer who had taken a 250 micrograms/kg dose of ivermectin. High mortality was recorded in mosquitoes feeding during the first week after treatment of the volunteer, for instance 100-80% failed to survive 3 days. A long-term residual effect of ivermectin in the blood was indicated by a small but significantly higher mortality in mosquitoes fed 6 weeks after ivermectin was taken. These effects were included in malaria transmission models that incorporated host choice and host-induced mortality parameters. For the zoophilic An. farauti, ivermectin treatment of animals resulted in a greater reduction in malaria than ivermectin treatment of humans alone, whereas for an anthropophilic vector, treatment of humans was more important. This suggests that ivermectin treatment of animals could have an important role in malaria control where An. farauti is the vector. Improvement in the health of humans and domestic animals through control of parasitic worms and mites might encourage community participation in strategies involving ivermectin.

Control measures against bancroftian filariasis in coastal villages in Tanzania.

Control measures against Bancroftian filariasis were implemented in four coastal villages in Tanzania.In two villages the mass administration of diethylcarbamazine in spaced doses over six months (total dose 54 to 72 mg kg−1 per person), reduced the infective bites per person per year from 189 to 13 and 41 to nil, respectively, despite a persistent microfilaraemia in the villagers of 3·8%. In a third village, larviciding with chlorpyrifos against Culex pipiens quinquefasciatus in pit latrines reduced the infective bites from 187 to 12. The corresponding reduction was from 24 to nine in a fourth village, where the control procedures integrated simple environmental measures with the use of larvicides (chlorpyrifos in pit-latrines and temephos to control Anopheles gambiae s.l. larvae in temporary pools).Because of the wide variation in transmission patterns within the same geographical area and even in the same locality in that area at different times a flexible approach to filariasis control is necessary. I...

Descriptions of the Anopheles (Cellia) farauti complex of sibling species (Diptera: Culicidae) in Australia

Descriptions of the three sibling species of the Anopheles farauti complex in Australia, A. farauti Laveran (formerly A. farauti No. 1), A. hinesorum Schmidt sp.n. (formerly A. farauti No. 2) and A. torresiensis Schmidt sp.n. (formerly A. farauti No. 3) are provided. These species form a part of the punctulatus group, which contains the major malaria vectors in the southwest Pacific. Morphological markers are described for adult females, fourth instar larvae and pupae which identify most specimens, and are presented in keys.

Population structure of the peridomestic mosquito Ochlerotatus notoscriptus in Australia

Abstract.  Ochlerotatus notoscriptus (Skuse) (Diptera: Culicidae) is the predominant peridomestic mosquito in Australia where it is the primary vector of dog heartworm, Dirofilaria immitis (Leidy), and a potentially important vector of arboviruses (Barmah Forest, Ross River) with geographical variation of vector competence. Although widespread, Oc. notoscriptus has low dispersal ability, so it may have isolated subpopulations. The identification of gene flow barriers may assist in understanding arbovirus epidemiology and disease risk, and for developing control strategies for this species. We investigated the population structure of Oc. notoscriptus from 17 sites around Australia, using up to 31 putative allozyme loci, 11 of which were polymorphic. We investigated the effect of larval environment and adult morphology on genetic variation. At least five subpopulations were found, four in New South Wales (NSW) and one unique to Darwin. Perth samples appear to be a product of recent colonization from the Australian east coast. For NSW sites, a Mantel test revealed an isolation by distance effect and spatial autocorrelation analysis revealed an area of effective gene flow of 67 km, which is high given the limited dispersal ability of this species. No consistent difference was observed between ‘urban’ and ‘sylvan’ habitats, which suggests frequent movement between these sites. However, a finer‐scaled habitat study at Darwin revealed small but significant allele frequency differences, including for Gpi. No fixed allozyme differences were detected for sex, size, integument colour or the colour of species‐diagnostic pale scales on the scutum. The domestic habit of Oc. notoscriptus and assisted dispersal have helped to homogenize this species geographically but population structure is still detectable on several levels associated with geographical variation of vector competence.

A morphological study of the Anopheles punctulatus group (Diptera: Culicidae) in the Solomon Islands, with a description of Anopheles (Cellia) irenicus Schmidt, sp.n.

A description of Anopheles (Cellia) irenicus Schmidt, sp.n. (formerly A. farauti No. 7) is provided. This species is one of six recorded from the Solomon Islands within the A. punctulatus group, which contains the major vectors of the causative agents of malaria and lymphatic filariasis in the southwest Pacific. Morphological markers are described for adult females, fourth-instar larvae and pupae that identify most specimens of A. irenicus. Keys are presented to distinguish members of the A. punctulatus group in the Solomon Islands.

Malaria control in central Malaita, Solomon Islands. 2. Local perceptions of the disease and practices for its treatment and prevention

Government health policy for malaria control in Solomon Islands has three main objectives: (1) early diagnosis and treatment of malaria at a health service; (2) reduction of human-vector contact through widespread use of insecticide-impregnated bed nets; and (3) provision of malaria chemoprophylaxis for pregnant women. Social research was carried out in thirteen villages in central Malaita to determine local attitudes toward malaria and to estimate the level of participation in malaria control activities. Interviews with 124 care-givers who had children 0-10 years of age, 20 focus group discussions and four evening structured observations were research methods used. Antimalarial drugs were the most favoured treatment, and use of traditional medicines and healers were reportedly minimal. Twenty-five percent of respondents reported keeping chloroquine at home and 42% said they would use chloroquine before seeking diagnosis and treatment from a health service. Structured observations suggest that protection against mosquitoes is poor during the evening. Fifty-two percent of respondents reported using fire and 32% said they used bed nets to protect themselves from mosquitoes. Participants had contradictory beliefs on the threat of malaria during pregnancy and the safety of taking chloroquine prophylaxis. Implications of malaria treatment and prevention practices are discussed, and recommendations for improving malaria control are presented.