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Simian foamy viruses (SFV) are ancient retroviruses of primates and have coevolved with their host species for as many as 30 million years. Although humans are not naturally infected with foamy virus, infection is occasionally acquired through interspecies transmission from nonhuman primates. We show that interspecies transmissions occur in a natural hunter-prey system, i.e., between wild chimpanzees and colobus monkeys, both of which harbor their own species-specific strains of SFV. Chimpanzees infected with chimpanzee SFV strains were shown to be coinfected with SFV from colobus monkeys, indicating that apes are susceptible to SFV superinfection, including highly divergent strains from other primate species.Simian foamy viruses (SFV) and their nonhuman primate hosts demonstrate coevolution (20). Despite the fact that SFV strains have been described for most Old World primate species, no human-specific foamy virus has yet been identified (16). However, zoonotic transmissions of SFV from various nonhuman primates to zookeepers and central African hunters or others having close contact with nonhuman primates are known to occur (5, 8-10, 21, 22). Such viruses have sequences that show a close relationship to SFV sequences from several nonhuman primate species (Fig. 1). Until now, it has been unclear whether such interspecies transmission can also take place when the hunter is naturally infected with its own species-specific SFV. Wild chimpanzees that regularly hunt and consume western red colobus monkeys (4) provide such a situation.Wild chimpanzees (Pan troglodytes verus) and western red colobus monkeys (Piliocolobus badius) sharing a rainforest habitat, the Taï National Park, Côte d'Ivoire, were tested for SFV infection. The chimpanzees have been under human observation for more than 25 years and are known individually as a result of a project focusing on wild chimpanzee behavior. Tissue samples were obtained from 14 chimpanzees that had died of anthrax, respiratory disease, or other causes (12,14,15). Samples of blood, collected in EDTA, from nine red colobus monkeys were obtained under anesthesia, and organ samples were collected from the remains of a further two that had been killed and eaten by chimpanzees (15). All represented adult animals.Using the SFV primers for the integrase gene (19), previous analyses revealed that 12 of the 14 chimpanzees harbored SFV strains (SFV cpz ) corresponding to strains described for the chimpanzee subspecies Pan troglodytes verus (details will be published elsewhere). Also 11 red colobus monkeys were tested positive for SFV using the same primers and standard conditions (96°C for 5 min; 40 cycles 96°C for 1 min, 56°C [first PCR] or 60°C [nested PCR] for 30 s, 72°C for 1 min; and a final elongation step at 72°C for 10 min). PCR products were purified using the QIAquick PCR purification kit (Qiagen) and sequenced directly in both directions without interim cloning.Phylogenetic analysis using the neighbor joining method (BioEdit, PHYLIP 3.572 package) of these 389-bp sequences ...

Onchocerciasis (river blindness) is a major parasitic disease of humans in sub-Saharan Africa caused by the microfilarial stage of the nematode Onchocerca volvulus. Using Onchocerca ochengi, a closely related species which infects cattle and is transmitted by the same black fly vector (Simulium damnosum sensu lato) as O. volvulus, we have conducted longitudinal studies after either natural field exposure or experimental infection to determine whether, and under what circumstances, protective immunity exists in onchocerciasis. On the basis of the adult worm burdens (nodules) observed, we determined that cattle reared in endemic areas without detectable parasites (putatively immune) were significantly less susceptible to heavy field challenge than agematched, naïve controls (P ‫؍‬ 0.002), whereas patently infected cattle, cured of infection by adulticide treatment with melarsomine, were fully susceptible. Cattle immunized with irradiated third-stage larvae were significantly protected against experimental challenge (100% reduction in median nodule load, P ‫؍‬ 0.003), and vaccination also conferred resistance to severe and prolonged field challenge (64% reduction in median nodule load, P ‫؍‬ 0.053; and a significant reduction in microfilarial positivity rates and density, P < 0.05). These results constitute evidence of protective immunity in a naturally evolved host-Onchocerca sp. relationship and provide proof-of-principle for immunoprophylaxis under experimental and field conditions. filariasis ͉ irradiation ͉ larvae ͉ ochengi ͉ Onchocerca