PubMed Health⌕ Search

Biomedical subjects

H Dagoro

Publications and source records attributed to H Dagoro.

15 recordsLinked to original sources
PubMed1999

Mass treatment with ivermectin for filariasis control in Papua New Guinea: impact on mosquito survival.

Field studies were carried out to determine the impact of mass human treatment with ivermectin on the survival of anthropophagic mosquitoes of the Anopheles punctulatus complex (Diptera: Culicidae), the vectors of lymphatic filariasis and malaria in Papua New Guinea. In a village where mass treatment had been given, using 400 microg/kg ivermectin plus 6 mg/kg diethylcarbamazine citrate (DEC), we performed pre- and post-treatment collections of freshly blood-engorged mosquitoes from the same nine bedrooms. All blood-fed mosquitoes collected less than 4 days after mass treatment died within 9 days, whereas 67% of those collected before treatment survived for >9 days. Comparison (using the log-rank test) of the survival curves for mosquitoes collected (i) before treatment, (ii)<4 days after treatment, and (iii) 28 days after treatment, showed the survival rate of group (ii) to be significantly lower than the other two (chi2=176, df=2, P<0.0001). Pre- and post-treatment all-night landing catches showed no reduction in human biting rates in the experimental village. In another village, where people were mass treated with ivermectin (400 microg/kg) only, the survival rates of freshly blood-engorged An. punctulatus collected from bedroom resting-sites less than 1 day after treatment, were compared to similar collections carried out at the same time in a nearby village where people were not treated with ivermectin. The 48-h survival rate for the ivermectin-treated village was 31% compared to 94% for the other; this difference was highly significant (chi2=32.42, df=1, P<0.0001). Mosquitoes fed 2 months post-treatment with DEC or collected 38 days post-treatment with ivermectin had normal survival rates. We conclude that the duration of the systemic lethal effect of ivermectin on mosquitoes is insufficient to be of epidemiological significance in filariasis control programmes that are based on biannual and annual single-dose treatments, but might reduce vectorial capacity sufficiently to block epidemics of dengue or even malaria.

Animals↗
PubMed1997

Transmission intensity and its relationship to infection and disease due to Wuchereria bancrofti in Papua New Guinea.

This study describes the relationship between transmission intensity and infection and disease due to Wuchereria bancrofti in an endemic area of Papua New Guinea. The prevalence of microfilaremia in the entire study population was 66%. Of 1892 persons examined, 6.2% and 12.3% had lymphedema of the legs and hydroceles, respectively. The prevalences of microfilaremia and clinical morbidity were lowest in persons <20 years old and increased progressively with age. Annual transmission potential and annual infective biting were monitored in five villages where Anopheles punctulatus and Anopheles koliensis are the only vectors of W. bancrofti. Both measures of the entomologic inoculation rate were positively associated with the village-specific microfilarial rate, mean intensity of microfilaremia, and prevalence of leg edema. These data indicate that transmission intensity is a major determinant of patent infection and morbidity rates in bancroftian filariasis.

Adolescent↗
PubMed1997

Health impact assessments of malaria and Ross River virus infection in the Southern Highlands Province of Papua New Guinea.

Malaria at an elevation of 1050 metres is common and highly endemic in the Tagari Valley in the Southern Highlands of Papua New Guinea. Health impact assessments showed that the risks of malaria and epidemic polyarthritis at a gasfield development project in this area were high. Baseline malariometric surveys were conducted in four villages in June and August 1990 and two follow-up surveys (May and December 1991) were made in the village of Nogolitogo near the gasfield pioneer base camp. A total of 941 blood smears were examined. Average malaria prevalence rates decreased with altitude from 56% (at 1050 m) to 9% (at 1700 m) for children 1-9 years of age and from 45% (at 1050 m) to 8% (at 1550 m) for those aged 10 years or more. The spleen rate for children less than 10 years old did not vary significantly with altitude, but average enlarged spleen for all ages decreased with altitude. Mean packed cell volume increased with altitude. Plasmodium falciparum was the most common malaria parasite found and Anopheles punctulatus the predominant vector. Ross River arbovirus (RRV) antibody prevalence was 59%. These results indicate frequent or constant transmission of malaria and pathogenic arboviruses. Entomological and epidemiological data suggested that the vulnerability of the valley community, the receptivity of the environment and the health hazards from malaria and RRV were high. Nonimmune Papua New Guineans and expatriate employees face high health hazards; therefore effective preventive measures are required to mitigate epidemics and avoid the likely heightened transmission of malaria and arboviruses caused by the development project.

Adolescent↗
PubMed1996

Transmission dynamics of Wuchereria bancrofti in East Sepik Province, Papua New Guinea.

Bancroftian filariasis is endemic in many areas of Papua New Guinea. This study describes the entomologic indices of transmission near Dreikikir in East Sepik Province, Papua New Guinea. A total of 1,735 culicine mosquitoes, including Culex and Mansonia species, were dissected, but none were infected with filarial larvae. In contrast, Anopheles punctulatus and An. koliensis were found to be potential vectors: 7.3% of Anopheles were infected and the mean number of first- to third-stage larvae per infected mosquito was 2.7. Transmission indices varied significantly in five villages located within a 50-km radius of each other. Annual biting rates ranged from 4,789 to 48,020 bites/person/year; annual infective biting rates from 15 to 836/person/year; and annual transmission potential from 31 to 2,340 third-stage larvae/person/year. Monthly transmission potential and monthly infective biting rate varied significantly in each village, with the highest indices of transmission observed in villages nearest sites where puddles formed in river beds during the dry season. These data indicate that there is small area variation in the intensity and temporal pattern of filariasis transmission and that culicine mosquitoes are not important vectors of W. bancrofti in this area.

Animals↗
PubMed1995

Filarial vector studies in a diethylcarbamazine-treated and in untreated villages in Papua New Guinea.

Entomological studies were undertaken in three villages in the East Sepik Province of Papua New Guinea. The inhabitants of one village, Nanaha, had been treated with diethylcarbamazine (DEC) to reduce the prevalence and density of microfilaraemia of Wuchereria bancrofti. No intervention was undertaken in the other two villages, Yauatong and Musenau, in which bancroftian filariasis was present but with markedly different human prevalence rates and mean parasite densities. In Yauatong, infection rates in anopheline vectors (Anopheles punctulatus and An. koliensis) varied from 20.5 to 46.6% with infectivity rates of 0-1.4% while these rates were 10.9-14.3% and 0-1.1% respectively in Culex quinquefasciatus. In Nanaha after DEC treatment, infection rates were as high as 16.3% in An. koliensis and infectivity rates reached 7.0% for An. punctulatus despite a 45% reduction in the number of people with detectable microfilariae (mf) and a 94% reduction in mf density in those who remained positive.

Animals↗
PubMed1994

The use of untreated bednets and malaria infection, morbidity and immunity.

The effect of bednet use was investigated, without undertaking a specific intervention, in four cross-sectional community-based surveys in 10 villages of a highly endemic area of Papua New Guinea. Over half (55%) of the villagers interviewed reported that they had used a bednet on the previous night. In general and after adjustment for age, village and housing characteristics, bednet users, particularly children, had lower parasite prevalences and spleen rates and less enlarged spleens than non-users. However, users were similar to non-users in terms of fever reported for the previous week, axillary temperature, parasite density and haemoglobin level. The prevalence of antibody to the ring erythrocyte surface antigen and the major merozoite surface antigen 2 was lower in users than non-users. The association with malariometric indices and immune responses remained significant when bednet users were compared with non-users in houses without bednets. Thus, untreated bednets do not reduce malaria transmission sufficiently to decrease morbidity. They might paradoxically increase the risk of clinical malaria by lowering the development of humoral immunity.

Adolescent↗
PubMed1993

Allozyme analysis reveals six species within the Anopheles punctulatus complex of mosquitoes in Papua New Guinea.

Among samples collected from nineteen localities in Papua New Guinea, we have identified six species within the Anopheles punctulatus complex of mosquitoes, by means of cellulose acetate allozyme electrophoresis. An.punctulatus Dönitz sensu stricto was collected from seven villages in the Madang area and from Buksak, Sausi Mission and an area 18 km SW of Tari; An.koliensis Owen from eight villages in the Madang area, from Popondetta and Brown River near Karema; and An.farauti No. 1 from ten coastal areas including Madang, Lorengau, Popondetta, Port Moresby, Rabaul and Wewak. Three newly recognized species, reported here for the first time, are designated as An.farauti No. 4 from Gonoa and Hudini, Madang area; An.farauti No. 5 from Ketarabo near Goroka; and An.farauti No. 6 from Hiwanda near Tari. Three other known members of the complex, An.clowi Rozeboom & Knight, An.farauti No. 2 (Bryan, 1973) and An.farauti No. 3 (Mahon & Meithke, 1982) were not detected in Papua New Guinea. Problems arising with morphological characters for the identification of species in this group are discussed.

Alleles↗
PubMed1990

The prevalence of naturally acquired multiple infections of Wuchereria bancrofti and human malarias in anophelines.

Malaria and filaria infection rates were determined for anopheline mosquitoes collected whilst biting and resting in village houses in Papua New Guinea. The number of anophelines infected with both parasites was greater than expected from the infection rates of each parasite and this difference was significant in resting collections. The excess of multiply infected mosquitoes is probably a result of a vector population composed of individuals with differing numbers of opportunities to become infected. Malaria-positive Anopheles punctulatus from resting catches had a significantly greater number of Stage 3 Wuchereria bancrofti larvae than malaria-negative mosquitoes. However, multiply infected mosquitoes appear to suffer greater mortality than non-infected or singly infected mosquitoes when the filarial worm reaches the third stage. Any potential increase in transmission resulting from multiple infections is thereby offset by a greater mortality rate in these mosquitoes.

Animals↗
PubMedDate not supplied

Effects of untreated bed nets on the transmission of Plasmodium falciparum, P. vivax and Wuchereria bancrofti in Papua New Guinea.

The impact of untreated bed nets on the transmission of human malaria and filariasis in a village in a hyperendemic area of Papua New Guinea was studied. In anopheline mosquitoes, the Plasmodium falciparum sporozoite antigen positivity rate, filarial infection rates and human blood indices dropped significantly after bed nets were introduced. This reduction in human-vector contact did not affect mosquito density as no significant difference in either landing rates or indoor resting catches was found. The number of bed nets in a house and ownership of dogs were factors significantly associated with a reduction in the number of indoor resting mosquitoes. However, the reduction in the P. falciparum sporozoite antigen rate in mosquitoes was not accompanied by a reduction in either malaria parasite or antibody prevalences or titres against the P. falciparum circumsporozoite protein.

Adolescent↗
PubMedDate not supplied

The epidemiology and control of lymphatic filariasis on Lihir Island, New Ireland Province.

Clinical, parasitological and entomological surveys performed in 9 villages on Lihir Island, Papua New Guinea, before mass treatment with diethylcarbamazine (DEC), showed that lymphatic filariasis, caused by nocturnally periodic Wuchereria bancrofti, was endemic in 8 of them. Blood samples from 593 people revealed an overall microfilarial carrier rate of 24%. Amongst endemic villages, microfilarial carrier rates ranged from 5% to 43% and there was no significant difference in parasite prevalence between males and females. Obstructive filarial disease, defined as lymphoedema of the limbs or hydrocele, was observed in only 2% of 262 males examined. None of the 265 females examined had clinical symptoms. Entomological surveys yielded a total of 4095 mosquitoes including 3,692 anophelines and 241 culicines but only Anopheles farauti was found to harbour infective larvae of W. bancrofti. Pretreatment infection and infective rates of An. farauti were 7% and 1% respectively and up to 12 infective larvae were found in a single specimen. The microfilarial carrier rate in a cohort of people who received two DEC treatments dropped from 59% to 32% but the difference was not statistically significant. However, density of microfilaraemia decreased significantly from 170 to 10 mf/ml. Biannual mass treatment with DEC significantly reduced vector infection rates and transmission intensity on Lihir.

Diethylcarbamazine↗