A malariometric survey in a rural community in the Muheza district, Tanzania: age profiles in the development of humoral immune responses.

A malariometric survey was carried out in a rural community situated in a malaria holoendemic endemic area of Tanzania. A random sample (n = 228) of different age groups was taken to elucidate the association between anti-Pf155/RESA and anti-Pf332 antibody responses and classical malaria indices. Parasitaemia, fever, splenomegaly, haematocrit and antimalarial consumption were assessed. Antibody responses against Pf155/RESA and Pf332 peptides were determined by ELISA. The age profiles of parasite density, splenomegaly, fever, haematocrit values and prevalence of antibody responses indicated intensive malaria exposure and the highest impact of malaria in small children. Forty-five percent of the study population had detectable chloroquine and desethyl-chloroquine blood levels, and the highest frequency and concentrations were recorded in the 12-23 months old. There was no significant association between the presence of drug and parasite density in the different age groups, although in the < 15 years old there was lower parasite prevalence among the children positive for drug in their blood (P < 0.05). High prevalence of antibody responses to all antigens was observed already at an early age, but the mean anti-Pf155/RESA and anti-Pf332 antibody levels increased significantly only in the adult group (P < 0.01). Significantly lower mean parasite densities were observed in high responders to Pf155/RESA and Pf332 peptides for the > or = 10 years old. For the 1-9 years, a similar difference was only observed in the high responders to Pf332. For the whole material, anti-Pf155/RESA and anti-Pf332 antibody levels correlated positively with age. When the effect of age was allowed for in analysing the relationship between parasite density and antibody level against the different antigens, a significant negative correlation was found only with regard to Pf332 in the > = 10 years age group. These results suggest that anti-Pf332 antibodies appear to be a better indicator for antiparasitic immunity, but both antigens are important for immune protection.

Periodicity of Dirofilaria immitis microfilariae in a dog from Muheza district, Tanzania.

Dirofilaria immitis (the dog heartworm) microfilarial periodicity was determined hourly for five days in an infected dog from Kambai village in Muheza district Tanzania. Maximal microfilarial counts were found at 1100 h and minimal at 2200 h. This finding represents the first record of D. immitis microfilarial periodicity in Tanzania.

Introduction to, and evaluation of, immunoassays in a malaria research institute in Tanzania.

Various immunoassays have been introduced into, and evaluated at, the Amani Medical Centre in north-east Tanzania. These include immunoblotting to identify mosquito bloodmeals, immunoradiometric and immunoenzymatic assays to assess the presence of circumsporozoite protein in mosquitoes, and enzyme-linked immunosorbent assays to measure antibodies to circumsporozoite antibody in people. The assays were shown to be reliable and practicable for use in the study of malaria epidemiology.

The changed pattern of malaria endemicity and transmission at Amani in the eastern Usambara mountains, north-eastern Tanzania.

Parasitological and entomological studies on malaria were conducted between 1980 and 1982 on the Amani hills in the eastern Usambara mountains of north-eastern Tanzania. Malaria vectors were scarce on the Amani hills until the late 1960s and it was generally presumed that any cases of malaria transmission must have been contracted by people while visiting lower altitudes where malaria is holoendemic. However, the malaria vectors Anopheles funestus and An. gambiae have both become more abundant during the 1970s and 1980s and sporozoite-positive specimens of both have been found. Malaria asexual parasite rates have been shown to have increased, for instance from 52.7% in 1980 to 53.8% and 63.7% in 1981 and 1982, respectively. The percentage of parasitized children aged below 1 year whose parents report that they have not visited lowland localities away from the Amani hills has increased, from 71.4% in 1980 to 80.0% and 91.0% in 1981 and 1982, respectively, suggesting possible local malaria acquisition. These parameters have been confirmed by increasing sporozoite rates from 0.0% in 1967-1971 to 0.09% in May-June 1973 and 11.1% in August and December 1980. Various factors including climatological changes and increased agricultural activities are attributable to this changed malaria endemicity and transmission.

Prospects of human malaria and Bancroftian filariasis infections in the Lower Rufiji Basin, Tanzania. I. Malaria.

Surveys for human malaria infections were conducted in the Lower Rufiji Basin in Tanzania, before and after the long rains in 1981. A multipurpose water resources development project has been planned in the area. Overall asexual malaria parasite, gametocyte and spleen rates of 38.6%, 3.8% and 21.1% respectively were observed before the long rains whilst respective parameters after the long rains were 44.5%, 2.8% and 17.3%. Malaria parasite species percentages of 95.5, 1.0, 0.2 and 3.4 were observed in respect of P. falciparum, P. malariae, P. ovale and mixed infections respectively for both periods. Malaria endemicity in the Lower Rufiji Basin ranges between mesoendemic to hyperendemic. Following implementation of the project, malaria is likely to become holoendemic.

Prospects of human malaria and Bancroftian filariasis infections in the Lower Rufiji Basin, Tanzania II. Bancroftian filariasis.

Surveys for human bancroftian filariasis infections were conducted in the Lower Rufiji Basin, Tanzania, before and after the long rains in 1981. A multipurpose water resources development project has been planned in the area. A microfilarial rate of 18.1%, a mean microfilarial count of 80 microfilariae per 100 microliters blood were observed. Generally, males showed higher microfilarial rates than their female counterparts. All microfilariae were identified as Wuchereria bancrofti. A prevalence rate of 0.4% was recorded for leg elephantiasis. None of the cases were seen in individuals below 20 years of age. Only two cases of elephantiasis of the breasts were seen and no cases of elephantiasis of the arms were encountered. Rates for scrotal elephantiasis and hydrocoeles in males were 8.7% and 11.5% respectively, and enlargement of the inguinal and/or femoral lymph glands was common and the onset of this manifestation is early.

Malaria in the Pare area of Tanzania. V. Malaria 20 years after the end of residual insecticide spraying.

A malariometric survey, including serology, was done in the South Pare area of the former Pare-Taveta Malaria Scheme, Tanzania, 10 years after the previous survey and 20 years after the end of residual insecticide spraying. Although the densities of the vectors and their infectivity rates have for 10 years equalled those found before malaria control, malaria in the human population is still significantly less. The chief factor in this delayed resurgence is though to be the increasing use of antimalaria drugs by the population.

Specificity of the indirect haemagglutination test with Plasmodium falciparum test cells. Comparison of indirect haemagglutination and fluorescent antibody tests on African sera.

The specificity of the indirect haemagglutination (IHA) test with Plasmodium falciparum placental antigen-sensitized test cells was examined with sera from healthy blood donors and from patients with diseases other than malaria. Only 1 nonspecific antibody reaction was seen in more than 700 tests. A comparison of IHA titres and indirect fluorescent antibody (IFA) titres with IgG and IgM conjugates on 503 sera from inhabitants of Mto Wa Mbu in Tanzania showed in successive age groups an increasing number of seropositive reactors with both tests. The increase in the proportion of positive reactions and in the mean titre levels started earlier but was more gradual in the IFA test than in the IHA test. Parasite carriers had higher antibody levels than people without an apparent parasitaemia. Parasite carriers in the younger age groups especially were more frequently seronegative in the IHA test than in the IFA test with anti-IgG conjugates. The reactivity of the IHA test with P. falciparum (Palo Alto/Aotus) antigen was higher than that with P. falciparum placental antigen and was thus closer to that of the IFA test with IgG conjugates.