Infection with Tickborne Parasite May Suppress Malaria

A new study suggests that monkeys chronically infected with babesiosis, a tick-borne parasite, are able to suppress malaria infection when exposed to a simian malaria parasite. The researchers from the Biomedical Primate Research Center, Rijswijk, The Netherlands report their findings in the March 2010 issue of the journal Infection and Immunity.

Babesia parasites are known to infect a wide variety of mammalian hosts and awareness of the role these organisms play as zoonotic agents of human disease is growing. Of the population infected with Babesia microti, 25 percent of adults and 50 percent of children remain asymptomatic. Human malaria is caused by four different Plasmodium species, however, Plasmodium falciparum and Plasmodium vivax are the most significant with P. falciparum attributed to more than 1 million deaths annually in sub-Saharan Africa.

Prior studies of Babesia and Plasmodium co-infection in rodents have reported induced cross-protection. In an attempt to confirm their prior report that a rhesus macaque chronically infected with B. microti was able to suppress infection with Plasmodium cynomolgi (a parasite of macaques with attributes similar to P. vivax), researchers infected six naive monkeys with B. microti and then 24 days later challenged four of them plus four naïve monkeys with P. cynomolgi blood-stage parasites. Results showed a significant decrease in P. cynomolgi infection in monkeys coinfected with B. microti.

"We conclude that ongoing infection with B. microti parasites leads to suppression of malaria infection," say the researchers.

Reference: L.M. van Duivenvoorde, A. Voorberg-van der Wel, N.M. van der Werff, G. Braskamp, E.J. Remarque, I. Kondova, C.H.M. Kocken, A.W. Thomas. 2010. Suppression of Plasmodium cynomolgi in rhesus macaques by coinfection with Babesia microti. Infection and Immunity, 78. 3: 1032-1039.