Salvador II strain of Plasmodium vivax in Aotus monkeys and mosquitoes for transmission-blocking vaccine trials.

Infections with the Salvador II strain of Plasmodium vivax in Aotus lemurinus griseimambra monkeys were fed upon by Anopheles freeborni mosquitoes. Periods of mosquito infectivity were determined to establish a model system for the testing of transmission-blocking vaccines. The highest levels of mosquito infection were associated with the ascending asexual parasitemia after reaching 1,000/microl, and before the peak asexual parasite count. Sporozoite-induced infections were more infectious than were trophozoite-induced infections. Secondary episodes of parasitemia were also infectious, indicating the lack of development of naturally developing transmission-blocking immunity to this strain of P. vivax in splenectomized Aotus monkeys following single infections.

Studies on a primaquine-tolerant strain of Plasmodium vivax from Brazil in Aotus and Saimiri monkeys.

A nonimmune American acquired an infection of Plasmodium vivax Type 1 malaria in Brazil in 1994. After returning to the U.S.A., he had a primary attack followed by 3 relapses. The primary attack and first 2 relapses were treated with a standard regimen of chloroquine, followed by 14 days of primaquine (15 mg/day). Following the third relapse, the primaquine treatment was extended to 28 days. No further relapses occurred. The lack of response to primaquine by this strain may recommend it as a suitable candidate for chemotherapeutic study if it can be adapted to an animal model. Anopheles quadrimaculatus mosquitoes infected by feeding on the patient during the first relapse were used to establish the strain in Aotus and Saimiri monkeys. Monkeys supported well the development of long-lasting parasitemia. Anopheles freeborni, Anopheles stephensi, and Anopheles gambiae mosquitoes were readily infected by feeding on the monkeys and by membrane feeding on diluted blood. Monkey-to-monkey transmission was obtained via the bites of infected mosquitoes and the intravenous injection of sporozoites dissected from salivary glands. This parasite is designated as the Brazil I/CDC strain of P. vivax.

The Santa Lucia strain of Plasmodium falciparum as a model for vaccine studies. I. Development in Aotus lemurinus griseimembra monkeys.

The Santa Lucia strain of Plasmodium falciparum and the Aotus lemurinus griseimembra monkey are proposed as models for the testing of sporozoite vaccines and transmission-blocking vaccines. Approximately 85% of splenectomized monkeys were infected when fed upon by 10 or more heavily infected Anopheles freeborni mosquitoes. Sporozoite-induced infections in monkeys with or without previous infection with P. vivax readily infected mosquitoes, thus making them candidates for testing transmission-blocking vaccines.

The Santa Lucia strain of Plasmodium falciparum as a model for vaccine studies. II. Development of Aotus vociferans as a model for testing transmission-blocking vaccines.

The Santa Lucia strain of Plasmodium falciparum and the Aotus vociferans monkey were studied as models for the testing of transmission-blocking vaccines. Virulence developed early in the passage history. Despite the use of only small quantities of chlorguanide and/or quinine to control infection coupled with the use of small inocula and delays in splenectomy, mosquito infection was markedly reduced from that seen during primary passage to this species of Aotus. It appears that the model may be most useful during its initial passage from the primary species, Aotus lemurinus griseimembra.

Further studies on the sporozoite transmission of the Salvador I strain of Plasmodium vivax.

Different species of Saimiri and Aotus monkeys were inoculated with sporozoites of the Salvador I strain of Plasmodium vivax. Of 58 Saimiri inoculated, 45 developed parasitemia (4 following bites and 41 following intravenous inoculation). Prepatent periods ranged from 10 to 63 days. Twelve of 19 monkeys inoculated with sporozoites that had been stored frozen developed patent parasitemia after 16-53 days. Of 41 Aotus monkeys inoculated, only 10 (2 via bites and 8 via intravenous inoculation) developed parasitemia. One of 7 Aotus inoculated with sporozoites that had been frozen developed parasitemia with a prepatent period of 26 days. Mosquitoes were infected by feeding on gametocytes from Aotus and Saimiri monkeys, chimpanzees, and a human. Sporozoites from Anopheles stephensi, Anopheles freeborni, Anopheles dirus, and Anopheles gambiae induced infection.

Experimental infection of Anopheles gambiae s.s., Anopheles freeborni and Anopheles stephensi with Plasmodium malariae and Plasmodium brasilianum.

Susceptibility to infection of 2 strains of Anopheles gambiae s.s., An. freeborni and An. stephensi, was determined for 2 closely related malaria parasites, Plasmodium malariae and P. brasilianum. Neither strain of An. gambiae supported development of oocyst densities as great as the other 2 anopheline mosquitoes. The ZAN strain of An. gambiae s.s. from Zanzibar was more susceptible to infection with the strain of P. malariae from Uganda than the G-3 strain of An. gambiae s.s. from The Gambia. All species and strains of mosquitoes supported complete development to the presence of sporozoites in the salivary glands.

The Peruvian III strain of Plasmodium brasilianum in Saimiri sciureus boliviensis monkeys.

A strain of Plasmodium brasilianum was isolated from a naturally infected Saimiri monkey from Peru and subsequently passaged to 21 splenectomized Saimiri sciureus boliviensis monkeys. Nine of 12 attempts to transmit infection by sporozoite inoculation were successful with prepatent periods ranging from 23 to 41 days. Gametocytes were infective to Anopheles freeborni, Anopheles stephensi, Anopheles dirus, Anopheles maculatus, and Anopheles gambiae mosquitoes. The strain demonstrated a high level of resistance to cure with chloroquine.