Studies on the Cambodian I strain of Plasmodium falciparum in Aotus monkeys.

The Cambodian I strain of Plasmodium falciparum, originally from Kampuchea was adapted for development in three different types of Aotus monkeys. High-level parasitemias were readily produced in splenectomized Colombian A. trivirgatus griseimembra monkeys. Initially, only minimal parasitemias developed in A. t. trivirgatus monkeys from Colombia. However, in one animal, adaptation occurred and high-level parasitemias were obtained during the second recrudescence of the infection. Passage to other A. t. trivirgatus monkeys indicated that the parasite was well adapted for development in splenectomized animals; low to moderate parasitemias were still produced in intact animals. This line of the parasite produced high level parasitemias when inoculated into splenectomized Aotus monkeys from Peru. Infections in Anopheles freeborni mosquitoes were obtained as late as the 7th passage in A. t. griseimembra monkeys and as late as the 7th recrudescence of the infection in an individual monkey (348 days after inoculation). The sporogonic cycle was completed in An. freeborni mosquitoes, and one transmission to an A. t. griseimembra monkey via the bites of infected mosquitoes was obtained.

Antibody response to heterologous and homologous antigens in Brugia malayi- and B. pahangi-infected Mongolian jirds as measured by the enzyme-linked immunosorbent assay (ELISA).

Sequentially collected sera from Mongolian jirds (Meriones unguiculatus) infected with Brugia malayi and B. pahangi were tested for antibodies to homologous and heterologous antigens by the enzyme-linked immunosorbent assay (ELISA). Titers were less than 1:100 prior to infection and rose rapidly (within 2 weeks). Peak titers were observed prior to patent microfilaremia, and high titers persisted during infection. Use of the homologous antigen did not increase sensitivity or specificity of the ELISA. In fact, B. malayi-infected jirds demonstrated higher titers to the heterologous antigen, B. pahangi, than to the homologous antigen. Fractionation of B. malayi antigen over a wide pH range using isoelectric focusing did not eliminate cross-reactions, but the reactions of 20 B. malayi sera and 20 B. pahangi sera tested more strongly to specific fractions, particularly in the lower pH range.

Susceptibility of Peruvian Aotus monkeys to infection with different species of Plasmodium.

Splenectomized Aotus trivirgatus monkeys of Peruvian origin were tested for their susceptibility to infection with different species of Plasmodium. Strains of P. vivax from Vietnam and El Salvador produced infections in eight animals with maximum parasite densities ranging from 2,000-180,000 per mm3. A strain of P. falciparum from Cambodia produced maximum parasitemias in five animals ranging from 8-25% of the red blood cells infected. Although two monkeys inoculated with P. fragile had maximum parasitemias of 31% and 42%, treatment was not necessary for animal survival. Three monkeys infected with P. knowlesi via the bites of infected mosquitoes had maximum parasitemias of from 25-41%; these animals died of their infections. Nine animals were infected with P. cynomolgi; maximum parasitemias in seven of these animals with no prior history of malarial infection ranged from 49,500 per mm3 to 11%; two animals with prior experience with P. vivax and P. fragile had maximum P. cynomolgi parasitemias of 65 and 13,200 per mm3. No infections were obtained in animals inoculated with P. coatneyi or P. hylobati.

Infection and transmission studies with Plasmodium gonderi in the Macaca mulatta monkey.

Eight different anophelines--Anopheles freeborni, An. maculatus, An. dirus, An. stephensi, An. atroparvus, An. sundaicus, An. quadrimaculatus, and An. albimanus--were shown to be susceptible to infection with a strain of Plasmodium gonderi from the drill. Mandrillus leucophaeus. Transmission was obtained via the bites of An. freeborni, An. maculatus, An. stephensi, and An. dirus mosquitoes to Macaca mulatta. Prepatent periods in Macaca mulatta monkeys following sporozoite inoculation ranged from 7 to 15 days with a median of 12.5 days. Relapses from fixed-tissue stages following treatment with chloroquine or quinine sulfate were not demonstrated.

Chemotherapy of Babesia microti infections in Mongolian Jirds.

For identifying drugs which might be effective in the treatment of human Babesia microti infections, 20 selected antiprotozoal agents or combinations of agents were tested for activity against B. microti in Mongolian jirds (meriones unguiculatus). 4-Methyl-primaquine and aromatic diamidines, including diminazene and pentamidine, were the most effective compounds tested.

The Chesson strain of Plasmodium vivax in Aotus monkeys and anopheline mosquitoes.

The Chesson strain of Plasmodium vivax was studied in Aotus trivirgatus monkeys. Parasitemia in intact and splenectomized animals was similar to that reported for this strain in man. Comparative infectivity studies with mosquitoes fed on infected monkeys indicated that the most susceptible was Anopheles freeborni, followed by An. balabacensis, An. culicifacies, An. maculatus, An. atroparvus, An. stephensi, An. quadrimaculatus, and An. albimanus. Transmissions via sporozoites from An. maculatus was demonstrated on two occasions; prepatent periods were 30 and 32 days.

Transmission of Plasmodium vivax from Vietnam by four different anophelines.

Infections of the SV-I strain of Plasmodium vivax from Vietnam were transmitted via the bites of infected Anopheles stephensi, An. maculatus, and An. balabacensis balabacensis mosquitoes. Infected salivary glands were also found in An. freeborni mosquitoes. In 18 successful transmissions, prepatent periods ranged from 10--17 days. Four black volunteers failed to develop infections even though they were fed upon by heavily infected An. maculatus and An. b. balabacensis mosquitoes.

Infectivity of Plasmodium simium to Aotus trivirgatus monkeys and different anophelines.

Infections of Plasmodium simium were induced in splenectomized and intact Aotus trivirgatus griseimembra monkeys by parasitized blood and by sporozoites from Anopheles freeborni mosquitoes. Eleven of 13 monkeys developed infection after sporozoite inoculation; prepatent periods ranged from 11 to 25 days (mean 15.8 days). Comparative infectivity studies indicated that An, freeborni mosquitoes were the most susceptible followed by An. stephensi, An. Balabacensis balabacensis, An. maculatus, An. quadrimaculatus, An. culicifacies, and An. albimanus. Studies with 3 pupal phenotypes of An. freeborni indicated that lines containing the green and nonstriped pupal phenotypes were more susceptible than the base colony; the striped phenotype was slightly less susceptible.

Infection and transmission studies with Plasmodium simiovale in the Macaca mulatta monkey.

Six different anophelines--Anopheles freeborni, An. b. balabacensis, An. maculatus, An. stephensi, An. atroparvus, and An. quadrimaculatus--were shown to be susceptible to infection with Plasmodium simiovale when fed upon splenectomized Macaca mulatta monkeys between the 1st and 26th days of patent parasitemia. Transmission was obtained via the bites of An. b. balabacensis and An. maculatus mosquitoes. Prepatent periods in M. mulatta monkeys following sporozoite inoculation ranged from 11 to 20 days with a median of 14 days.

Attempts to immunize monkeys against Plasmodium knowlesi by using heat-stable, serum-soluble antigens.

Thirty-six Macaca mulatta monkeys were immunized with different concentrations and regimens of heat-stable, serum-soluble (S-) antigens of Plasmodium knowlesi prior to challenge with the homologous parasite via sporozoite inoculation. Fewer deaths and reduced maximum parasitemias occurred in those animals inoculated with 10 to 40 mg of S-antigen compared to nonimmunized monkeys or those receiving only Freund's adjuvant. Protection was incomplete, however, suggesting that atibodies to S-antigens may have a limited role in protection of hosts to malarial infection.

Development of different strains of Plasmodium vivax in two species of Anopheles.

Anopheles freeborni mosquitoes with oocyst infections had salivary gland infections at a higher rate of Plasmodium vivax from the New World than with strains from Asia, particularly those from South Vietnam. Anopheles maculatus mosquitoes supported development from oocysts to heavily infected salivary glands for all the strains of P. vivax tested. The results suggest that P. vivax introduced from Vietnam would be less likely to be transmitted by native A. freeborni mosiquitoes than would malaria from some other areas.

Studies on human malaria in Aotus monkeys. VI. Infectivity of Plasmodium malariae to different Anophelines.

Anopheles freeborni, A. balabacensis balabacensis, A. atroparvus, A. stephensi, and A. maculatus mosquitoes were infected by feeding on 12 Aotus trivirgatus monkeys infected with a Nigerian strain of Plasmodium malariae. Comparative infectivity studies indicated that the first 2 species were the most heavily infected.