Biology of Monanema globulosa, a rodent filaria with skin-dwelling microfilariae

Abstract

ABSTRACTMonanema globulosa (Nematoda: Filarioidea) was recovered from four species of rodents in Kenya, with a prevalence of up to 94% in the striped mouse, Lemniscomys striatus. The adult worms are site-specific to the pulmonary arteries and release sheathed microfilariae that travel via the blood to the skin. Densities of microfilariea in the ears (mf/mg) were five to eight times greater than in any other region of the body and were directly proportional to the number of adult worms present. Highest concentrations of microfilariae in the skin were reached after 100 to 200 days and low numbers persisted in most animals for approximately 500 days.Third-stage larvae from ticks (Haemaphysalis leachii) injected subcutaneously into jirds migrated widely through the body during early development. Moults occurred twice, after 5 to 10 days and 25 days, and the mean prepatent period was 75 (range 69 to 88) days. A mild eosinophilia developed which peaked after 29 days. Adults in the lungs provoked widespread and intense perivascular cuffing and more localized hypertrophy and fibrosis of the intima in arterioles. Dead adults caused granulomata which obliterated smaller vessels. Microfilariae in the skin elicited no local tissue reaction, but some which invaded the eyes caused a monocyte infiltration of the cornea. It is concluded that the parasite is well adapted to its natural hosts and that it has potential as a rodent model for human onchocerciasis because of the localization of microfilariae in the skin.