Radical cure of Chesson strain vivax malaria in man by 7, not 14, days of treatment with primaquine

Glucose-6-phosphate dehydrogenase-normal adult volunteers infected with mosquito-bone Chesson strain vivax malaria were treated with chloroquine and primaquine during the initial attack. Administration of 60 mg (base) of primaquine daily for 7 days was as effective in preventing relapse as is the regimen customarily used for the radical cure of infections produced by this strain, namely, 30 mg daily for 14 days. However, it is stressed that because of the risk of primaquine-induced hemolysis in individuals having genetically-transmitted erythrocyte abnormalities this high dosage should not be used routinely.

The treatment of malaria

At least four doses of quinine followed by a single dose of mefloquine or by a single dose of sulfadoxine-pyrimethamine are two highly effective regimens for chloroquine-resistant falciparum malaria. Mefloquine alone is valuable in ambulant patients. Chloroquine-sensitive falciparum malaria can be treated with a course of chloroquine. Vivax and all other types of malaria should be treated with sequential chloroquine and primaquine. Quinine, by intravenous infusion, is the most effective drug for severe falciparum malaria. The optimum intravenous dose varies between 5 mg/kg and 10 mg/kg administered over four hours. Intravenous or oral quinine should be administered about every 12 hours and the total daily dose of quinine should rarely exceed 20 mg/kg. Intravenous fluid input should be controlled in falciparum malaria to prevent pulmonary oedema. Established renal failure is best treated by dialysis. The value of adrenocortical steroids for falciparum coma has not been established. Fresh blood transfusion may be helpful in small doses for severe anaemia and to replace clotting factors. Anticoagulants, such as heparin, should not be used in falciparum malaria.

Evaluating new antimalarial drugs against trophozoite induced Plasmodium cynomolgi malaria in rhesus monkeys

An antimalarial drug testing system is described which utilizes trophozoite induced Plasmodium cynomolgi malaria in rhesus monkeys. The schizonticidal activity of standard antimalarial drugs in this system is reported. The system accurately predicted antimalarial activity in man of 8 of 9 compounds selected for clinical trials.

Chemotherapy of Plasmodium vivax in Saimiri and Aotus models

Three standard antimalarial compounds were tested against trophozoite or sporozoite induced infections of the Panamanian Achiote strain of Plasmodium vivax in two species of monkeys. In Saimiri sciureus (24 subjects) and Aotus trivirgatus (11 subjects), parasite clearance from the peripheral blood averaged 3 days after initiating chloroquine therapy (total dose of 25 mg base/kg body weight over 3 days or single dose of 10 mg base/kg. Trophozoite induced infections were cured in all of 10 Saimiri and all of 6 Aotus, as indicated by the absence of relapses. Relapses did occur in 3 of 11 tests with Saimiri and 3 of 5 tests with Aotus against sporozoite induced infections. Subpatent periods ranged from 38 to 111 days among intact and splenectomized hosts. This is the first chemotherapeutic evidence for the persistence of exoerythrocytic stages of P. vivax in New World monkeys. Pyrimethaminr (single dose of 1 mg/kg) cured trophozoite induced infections in all of five Saimiri hosts. Radical cure of sporozoite induced infections was accomplished in each of six trials with chloroquine (25 mg base/kg) plus primaquine (1 mg base/kg for 14 days). The primary attack or relapse was treated. These models warrant further investigation in chemotherapy.

Rodent systems (Plasmodium berghei-Anopheles Stephensi) for screening compounds for potential causal prophylaxis

An in vivo screening system is described in which drugs administered to rats or mice and challenged with sporozoites are evaluated for their antimalarial properties (causal prophylaxis, suppression, therapy) by the presence or absence of exoerythrocytic forms and parasitemia. The system is composed of A/J mice, Sprague-Dawley rats, Plasmodium berghei, and Anopheles stephensi. Good correlation has been found between test results and practical application.

Malaria in Birmingham 1968-73

During the years 1968 to 1973 70 patients suffering from malaria were admitted to one hospital in England. Twenty had malignant tertian malaria while the remainder had infections caused by Plasmodium vivax, P. ovale and P. malariae. Malaria should be suspected in every febrile patient who has visited a tropical country, and the diagnosis can be confirmed only by examining blood films. Disseminated intravascular coagulation may complicate the disease, and should be considered in every case.British workers spending short periods in malarious areas and Asian immigrants returning home for a holiday are often inadequately instructed about malarial prophylaxis, particularly the need to continue this for at least a month after they return home. Companies and travel agencies should be obliged to provide such instructions.

Imported malaria

There have been 4 waves of imported malaria in the USA. They occurred during the colonization of the country and during the Second World War, the UN Police Action in Korea, and the Viet-Nam conflict. The first 3 episodes are briefly described and the data on imported malaria from Viet-Nam are discussed in detail.Endemic malaria is resurgent in many tropical countries and international travel is also on the rise. This increases the likelihood of malaria being imported from an endemic area and introduced into a receptive area. The best defence for countries threatened by imported malaria is a vigorous surveillance programme. The principles of surveillance are discussed and an example of their application is provided by a description of the methods used to conduct surveillance of malaria in the USA.

Malaria

These discussions are selected from the weekly staff conferences in the Department of Medicine, University of California, San Francisco. Taken from transcriptions, they are prepared by Drs. David W. Martin, Jr., Assistant Professor of Medicine, and Kenneth A. Woeber, Associate Professor of Medicine, under the direction of Dr. Lloyd H. Smith, Jr., Professor of Medicine and Chairman of the Department of Medicine. Requests for reprints should be sent to the Department of Medicine, University of California, San Francisco, San Francisco, Ca. 94122.

Entopolypoides macaci, a Babesia-like parasite in Cercopithecus monkeys

A description is given of a Babesia-like parasite found in the erythrocytes of two Cercopithecus pygerythrus monkeys probably from East Africa. Morphologically it seems identical with a parasite found by Mayer (1934) in Macaca irus monkeys from Java and named by him Entopolypoides macaci. On the other hand, the present African type differs from the Javan one in that it does not readily infect M. irus or M. mulatta monkeys; and it might well be named provisionally E. macaci (cercopitheci). Morphologically, the early forms are fine rings with a large vacuole but the more mature parasites form several fine long processes which are best seen under phase-contrast illumination. The cycle in the erythrocytes probably ends by division into four new parasites and it takes 3 days to quadruple the number. There is no synchronicity, such as occurs with malaria. The parasite was passed by syringe into Erythrocebus patas, Papio papio and Cercocebus galeritus monkeys in which it produced a light parasitaemia if they were intact, or an intense one (up to 70% erythrocytes parasited) if they were splenectomized. In both cases the bouts of parasitaemia are prolonged for weeks, and they may continue with relapses apparently for years. A light transient infection was produced in one splenectomized Macaca mulatta and in one out of two intact M. irus monkeys, but not in one M. arctoides (splenectomized), one Cebus albifrons, one C. apella, two Aotus trivirgatus and two Pan troglodytes (one splenectomized). Apparently the parasite readily infected African lower primates, hardly infected Asiatic ones, and did not infect American ones. Even in susceptible splenectomized monkeys, in which it produced prolonged intense parasitaemia, the parasite causes little pathogenic effect beyond a moderate anaemia. Attempts were made to transmit it through Rhipicephalus sanguineus, Dermacentor andersoni, Ornithodoros (sp.), Ornithonyssus bacoti and Aedes aegypti but they were unsuccessful. Probably the vector is an Ixodid tick. Chemotherapeutically the parasite was sensitive to a babesicidal compound, Imidocarb (3,3′-bis-(2 imidazolin-2yl) carbanilide) and to primaquine but not to chloroquine, pyrimethamine, pentamidine, Berenil or homidium.