Jimmie C. Skinner

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.

Studies on the Santa Lucia (El Salvador) strain of Plasmodium falciparum in Aotus trivirgatus monkeys.

The Santa Lucia strain of Plasmodium falciparum was isolated from El Salvador, Central America, and established in Aotus trivirgatus monkeys. Transmission from monkey to monkey via the bites of infected Anopheles freeborni, A. maculatus, and A, albimanus mosquitoes was obtained in 20 of 27 attempts. Prepatent periods in the monkeys ranged from 17 to 46 days with a mean of 24.3 days. Parasitemias and mortality were higher following sporozoite inoculation into animals which had been previously infected with P. vivax than in those with no previous malaria experience. Monkeys previously infected with P. vivax and P. cynomolgi had lower maximum parasitemias than those previously infected with P. vivax only.

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.

Infectivity of the Santa Lucia (El Salvador) strain of Plasmodium falciparum to different anophelines.

Anopheles freeborni mosquitoes were much more heavily infected with the Santa Lucia strain of Plasmodium falciparum from coastal El Salvador than were any of the other species tested. Of 5 strains of A. albimanus examined, the most heavily infected was the CA-109A and the least was the Melara, both of which come from coastal El Salvador. Of the exotic anophelines, the A. maculatus was infected at a slightly higher level than was the A. balabacensis. The incidence of highly infected individual mosquitoes was greatest in the Panama-Escobal strain of A. albimanus from the Republic of Panama; the incidence was lowest in the Melara strain from El Salvador. All strains of A. albimanus developed infected salivary glands, but the A. freeborni and A. maculatus mosquitoes appeared to develop infected glands more effeciently. Infection rates in A. freeborni mosquitoes were highest if mosquitoes were fed on Aotus trivirgatus monkeys between the 19th and 25th days of patent gametocytemia.

STUDIES ON THE NORTH KOREAN STRAIN OF PLASMODIUM VIVAX IN AOTUS MONKEYS AND DIFFERENT ANOPHELINES

Twenty-two Aotus monkeys of different karyotypes were infected with the North Korean strain of Plasmodium vivax. Aotus lemurinus griseimembra animals from Colombia produced higher maximum parasitemias and more readily infected mosquitoes than did Aotus monkeys from Bolivia (K-VI) or Peru (K-V and K-X). Comparative feedings indicated that the most susceptible mosquito species was Anopheles stephensi, followed by An. gambiae, An. dirus, An. freeborni, An. quadrimaculatus, An. culicifacies, and An. maculatus.

THE SPOROGONIC CYCLE OF PLASMODIUM REICHENOWI

Plasmodium reichenowi, a malarial parasite of the chimpanzee, was infective to Anopheles freeborni, Anopheles quadrimaculatus, Anopheles stephensi, Anopheles maculatus, Anopheles dirus, and Anopheles culicifacies mosquitoes. Anopheles gambiae and Anopheles albimanus were not infected. Mean oocyst diameters of P. reichenowi were smaller than those of the other chimpanzee parasite, Plasmodium schwetzi. Sporozoites were present in the salivary glands of An. freeborni at 15 days when held at 25 to 26 C.

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.

SUSCEPTIBILITY OF MACACA FASCICULARIS MONKEYS FROM MAURITIUS TO DIFFERENT SPECIES OF PLASMODIUM

Macaca fascicularis monkeys from Mauritius were shown to be susceptible via sporozoite inoculation to 7 species of Plasmodium (P. fragile, P. coatneyi, P. gonderi, P. inui, P. cynomolgi, P. knowlesi, and P. fieldi), indigenous to macaques in southeastern Asia. Four monkeys were sequentially infected with different species of Plasmodium to determine maximum and course of parasitemia. In 2 nonsplenectomized monkeys, P. fragile developed maximum parasite counts of only 134 and 155/microliters. For Plasmodium knowlesi, a parasite that is life-threatening to rhesus monkeys, maximum parasite counts were 4,278 and 7,440/microliters. Plasmodium coatneyi developed to what must be considered as moderate levels. After animals underwent splenectomy, parasite counts of P. coatneyi were 58,280, 89,094, 4,464, and 43,524/microliters. The maximum parasite counts for P. gonderi (13,508 and 21,576/microliters) and P. fieldi (1,767 and 17,836/microliters) were lower than would be expected in M. mulatta. In 2 monkeys that developed patent parasitemia with P. inui, the maximum parasite counts (95,046 and 728,748/microliters) indicated that this parasite may be the best adapted species for development in these animals once infection is established. Finally, the reinfection of 2 monkeys with P. cynomolgi suggested that some animals may be basically more resistant than others, whether splenectomized or not, to the production of high-density parasitemia.

Infection of Peruvian Aotus nancymai Monkeys with Different Strains of Plasmodium falciparum, P. vivax, and P. malariae

Aotus nancymai (karyotype I) monkeys from Peru were studied for their susceptibility to infection with Plasmodium falciparum, P. vivax, and P. malariae. Three strains of P. falciparum (Santa Lucia from El Salvador, Indochina I/CDC from Thailand, and Uganda Palo Alto) were inoculated into 38 monkeys. The results indicated that this species of Aotus monkey is highly susceptible to infection. The Uganda Palo Alto and the Santa Lucia strain parasites appear to be the most useful for immunologic and chemotherapeutic studies. Five strains of P. vivax (Chesson, ONG, Vietnam Palo Alto, Salvador I, and Honduran I/CDC) were inoculated into 28 monkeys. The Vietnam Palo Alto strain produced the highest level parasitemias ranging from 23,800 to 157,000/mm3. Mosquito infections were obtained with the ONG, Chesson, and Salvador I strains. Two out of 6 attempts to transmit P. vivax via sporozoite inoculation to splenectomized monkeys were successful with prepatent periods of 39 and 57 days. Five monkeys were infected with the Uganda I/CDC strain of P. malariae. Maximum parasitemias ranged from 10 to 5,390/mm3.

Effect of sequential infection with Plasmodium vivax and P. falciparum in the Aotus trivirgatus monkey.

Aotus trivirgatus monkeys with prior experience with Plasmodium vivax were inoculated with P. falciparum via the bites of infected mosquitoes. The animals with prior malaria had higher parasitemias and significantly higher levels of mosquito infectivity than monkeys with no prior P. vivax experience. Monkeys with a history of P. falciparum that were inoculated with P. vivax had essentially the same parasitemias as those with no prior malaria. However, levels of mosquito infectivity were markedly increased in those monkeys with a history of P. falciparum. The results imply that the introduction of another malaria species into a malarious area may result in higher levels of mosquito infection and more rapid establishment and distribution of that species.