Alan Y. Huong

Impact on mortality and fertility of a community-based malaria control programme in Saradidi, Kenya.

Mortality and fertility rates were measured from 1981 to 1983 by prospective registration of vital events as part of a community-based malaria control and health development programme in Saradidi, Kenya. There was no obvious effect of providing chloroquine phosphate for treatment of malaria in each village on mortality or fertility rates. Crude death rates were 13.1 in the year before intervention (1 May 1981 to 30 April 1982) and 12.3 after intervention (1 September 1982 to 31 August 1983). Neonatal mortality increased from 36.8 per 1000 live births pre-intervention to 49.1 during intervention. There was a slight decline in post-neonatal (one to 12 months) mortality (72.8 to 67.0) and a significant drop in early childhood mortality (25.2 to 18.2). The change in mortality rates in these two age groups were fully explained by a high rate of measles mortality in the pre-intervention period. Measles accounted for 35.7% of 284 reported deaths in infants one to 12 months of age and for 40.9% of 230 deaths in children one to four years old. There was little change in reported malaria-specific mortality rates in infants and young children most likely because of a high level of chloroquine use for treatment of presumptive illness. Perinatal mortality by area ranged between 60.4 and 81.3 pre-intervention to 79.5 to 97.2 after the control programme was instituted. Crude birth rates by area remained stable at about 40 and general fertility rates were about 200. Both pre-intervention and during intervention infants were significantly more likely to have died without medical consultation than children one to four years. However, 79.2% of 284 infants and 90.7% of 193 children died in spite of having consulted a health worker prior to death. The data suggest that a measles vaccine programme would significantly reduce mortality rates in infants and young children. The fact that the majority of infants and young children died in spite of receiving medical attention indicates both the inadequacy of curative medical services in this high mortality setting as well as the necessity for promoting preventive health measures.

SPOROZOITE-INDUCED INFECTIONS OF THE SALVADOR I STRAIN OF PLASMODIUM VIVAX IN SAIMIRI SCIUREUS BOLIVIENSIS MONKEYS

Twenty Saimiri sciureus boliviensis monkeys from Bolivia were inoculated intravenously with sporozoites of the Salvador I strain of Plasmodium vivax. All animals were splenectomized 7 days after inoculation. Inoculation of 100,000 sporozoites resulted in prepatent periods averaging 16.6 days; all monkeys developed high-level parasitemias with an average maximum of 103,000 per mm3. Inoculation of 10,000 sporozoites resulted in average prepatent periods of 19.4 days; one of the resulting infections produced a transient low-level parasitemia. Of 5 monkeys inoculated with 1,000 sporozoites, 4 had prepatent periods of from 24 to 35 days and 1 failed to demonstrate any parasitemia; 1 monkey supported a low-level transient parasitemia, whereas the other 3 monkeys had high-level parasitemias. It is proposed that by using a minimum inoculum of 10,000 sporozoites, the model system may be useful in the testing of anti-sporozoite vaccines directed against P. vivax.

Community-based malaria control in Saradidi, Kenya: description of the programme and impact on parasitaemia rates and antimalarial antibodies.

A community-based malaria control programme initiated in Saradidi, Kenya in 1982 is described. Antimalarial treatment provided by volunteer community health workers was made available in each village. Malaria was holoendemic. Parasitaemia rates by age were high and did not change after the control programme began. Plasmodium falciparum was the most common species and was present alone or mixed in 98.2% of 8105 infections. Virtually all (98.5%) of 2040 blood samples collected in May 1981 were positive (reciprocal titre greater than or equal to 80) to P. falciparum by the indirect fluorescent antibody (IFA) test. Seropositivity rates to P. falciparum in the IFA test or the enzyme-linked immunosorbent assay (ELISA) were high in all age groups and did not change significantly in longitudinal surveys or in a cohort of children zero to nine years old followed at intervals. While the malaria control programme was successful in bringing treatment to each village, malaria prevalence was not reduced. Parasitologic and serologic studies alone were not adequate to describe the impact of the community-based malaria control programme in Saradidi. Morbidity and mortality rates caused by malaria can decline, significantly improving the health of the population, in the absence of any decrease in parasitaemia rates.

Malaria chemoprophylaxis to pregnant women provided by community health workers in Saradidi, Kenya. II. Effect on parasitaemia and haemoglobin levels

To determine the effects of chloroquine phosphate (300 mg base weekly) chemoprophylaxis for malaria provided by volunteer village health helpers (VHHs), pregnant women attending antenatal clinics in Saradidi, Kenya, were examined each month. Parasitaemia, haemoglobin level, and the presence of urinary 4-aminoquinolines were determined at each visit. The age composition and parity of women taking chemoprophylaxis were not statistically significantly different from those of the other women. A total of 104 (29.1%) of 357 pregnant women from 23 villages where chemprophylaxis was provided by VHHs said they were taking it. Women 30 to 44 years of age (43.9%) of 82) were more often taking prophylaxis than those younger (25.1% of 271) (P less than 0.0005). An additional 573 pregnant women to whom regular chemoprophylaxis was not provided from 33 control villages were also examined at least once. When compared with those from women not taking prophylaxis, blood samples from pregnant women on antimalarial prophylaxis had lower parasite rates (17.7% of 265 compared with 26.2% of 1700, P less than 0.005), higher haemoglobin levels (59.1% of 127 were greater than or equal to 10.0 g l-1 compared with 49.7% of 1111, P less than 0.05), and a higher mean haemoglobin level (9.95 g dl-1 compared with 9.62, P = 0.019) and urine samples were more often positive for 4-aminoquinolines (15.7% of 255 compared with 8.3% of 1656, P less than 0.0005). For women with two or more parasitologic samples, 69.6% of 79 pregnant women on prophylaxis had no parasites found on any visit compared with 51.6% of 516 women not on chemoprophylaxis (P less than 0.005).(ABSTRACT TRUNCATED AT 250 WORDS)

INFECTION OF AOTUS AZARAE BOLIVIENSIS MONKEYS WITH DIFFERENT STRAINS OF PLASMODIUM FALCIPARUM

Eleven strains of Plasmodium falciparum from Asia, Africa, and Central America were inoculated into a total of 58 splenectomized Aotus azarae boliviensis monkeys. Eight of the strains produced high-level parasitemias, whereas 3 (2 from Honduras and 1 from Zaire) produced only low-level parasitemias. Mosquito infections were only obtained during the first 2 linear passages of the Santa Lucia strain from El Salvador. The results indicate that this species of Aotus monkey is highly susceptible to infection with strains of P. falciparum from different geographic areas, and therefore may be useful for a number of chemotherapeutic or immunologic studies. Its usefulness for mosquito infection studies is very limited.

Malaria chemoprophylaxis to pregnant women provided by community health workers in Saradidi, Kenya. III. Serologic studies.

Parasitaemia and antimalarial antibodies were examined from May 1983 to March 1984 in monthly samples taken from 930 pregnant women attending antenatal clinics in Saradidi, Kenya, and 317 of their infants; 104 women were taking chloroquine phosphate 300 mg base weekly for chemoprophylaxis. Seropositivity rates in pregnant women were uniformly high, and mean enzyme-linked immunosorbent assay (ELISA) absorbance values were not related to presence of parasitaemia or history of chemoprophylaxis. Parasitaemia was present in 26.5% of 1677 slides from pregnant women and there was little variation by month of sample. Mean ELISA absorbance values varied by month of sample. Seropositivity rates in infants were high as measured in both the indirect fluorescent antibody (IFA) test (81.6% of 938) and ELISA at 1:100 (83.8% of 1025) and 1:1000 (34.8% of 1025) serum dilutions. Seropositivity rates decreased slightly after birth but by four months of age rates were again high. Parasitaemia was present in 26.5% of 1677 slides from pregnant women. Paired comparisons were made on maternal samples collected less than two months before parturition and samples from the infants collected within two months after birth. The paired antibody response by IFA or ELISA was not dependent on the presence of detectable parasitaemia in the mother. Infants from mothers with a history of antimalarial chemoprophylaxis had significantly (P = 0.04) lower IFA titres than other infants. Measuring the absorbance of a 1:100 serum dilution by ELISA appeared to be an excellent method with which to measure longitudinal serologic changes in a population.

OBSERVATIONS ON THE INFECTIVITY OF TWO STRAINS OF PLASMODIUM VIVAX FROM VIETNAMESE REFUGEES TO AOTUS MONKEYS AND ANOPHELINE MOSQUITOES

Two strains of Plasmodium vivax (NAM and ONG) were isolated from Vietnamese refugees and established in splenectomized Aotus monkeys from Colombia and Bolivia. Mosquito infections were readily obtained from animals with no prior malarial experience or with a history of infection with P. falciparum only. Those animals with previous infections with P. vivax supported only low parasitemias, and the mosquito infections were minimal. Complete development of the sporogonic cycle was obtained with all species of mosquitoes tested. The most susceptible mosquito was An. dirus. Other mosquitoes readily infected with these strains were An. culicifacies, An. maculatus, An. gambiae, An. stephensi, and the two North American species, An. freeborni and An. quadrimaculatus. Transmission from one monkey to another was obtained via the bites of infected An. dirus, An. stephensi, and An. maculatus mosquitoes.

STUDIES ON THE INDOCHINA I/CDC STRAIN OF PLASMODIUM FALCIPARUM IN COLOMBIAN AND BOLIVIAN AOTUS MONKEYS AND DIFFERENT ANOPHELINES

The Indochina I/CDC strain of Plasmodium falciparum was isolated from a physician returning to the United States after working in the refugee camps along the Thailand-Kampuchean border. The strain was established in splenectomized Aotus monkeys from Colombia after being grown in vitro for 50 days. During the first three passages in Colombian monkeys, the parasites were not infective to Bolivian Aotus monkeys. After six intervening passages in Saimiri sciureus monkeys, the parasites produced high parasitemias in both Colombian and Bolivian Aotus, but gametocytes were no longer produced. Mosquito infections were obtained only during the first three passages in the Colombian monkeys. The most susceptible mosquito was Anopheles freeborni, followed by An. dirus, An. stephensi, An. maculatus, An. culicifacies, and, rarely, An. gambiae. Sporozoites were found in the salivary glands of the An. freeborni, An. dirus, An. stephensi, and An. maculatus.

Consumption of chloroquine phosphate provided for treatment of malaria by volunteer village health workers in Saradidi, Kenya.

A community-based malaria control programme in Saradidi, Kenya provided chloroquine treatment for malaria in each village beginning in May 1982. Malaria was holoendemic in Saradidi. Treatment was provided by volunteer community health workers chosen and supported by the village. Consumption of the drug and characteristics of persons treated were recorded. Between 1 September 1982 to 31 August 1983, 40,649 treatments with chloroquine were given to village residents. The treatment rate per person in the mid-year population was 1.24. However, at least 41.8% of the mid-year population of 32,650 did not receive a single treatment. Multiple treatments were given to 50.5% of persons treated at least once and 13.4% of 13,879 persons treated at least once received five or more treatments during the year. Consumption patterns were not random: they were higher in females, in persons above 30 years of age and in the area with greater community organization and community participation. There is need to ascertain the reasons why so large a proportion of the population never received a single treatment in this highly malarious area and why adults who should not have had a high frequency of clinical malaria were treated so often. Nonetheless, the results demonstrate that volunteer community health workers can effectively provide treatment for malaria.

Studies on a newly isolated strain of Plasmodium brasilianum in Aotus and Saimiri monkeys and different anophelines.

A strain of Plasmodium brasilianum was isolated from an Aotus vociferans monkey from Peru. The parasite readily infected Aotus monkeys from Bolivia and Columbia and Saimiri sciureus monkeys from Peru and Bolivia. Highest level mosquito infections were obtained by feeding on the Saimiri monkeys. The most susceptible mosquito was Anopheles freeborni, followed by Anopheles dirus, Anopheles stephensi, Anopheles gambiae, Anopheles culicifacies, Anopheles maculatus and Anopheles albimanus. Anopheles quadrimaculatus were also susceptible to infection. Degenerating oocysts were observed in An. dirus mosquitoes infected with this parasite. Transmission via the bites of infected An. maculatus mosquitoes was obtained to 3 Bolivian Saimiri monkeys; prepatent periods were 27, 27, and 29 days.