[Filariasis of the eye: problems with animal models]

Twelve rodents (Mastomys natalensis and Meriones persicus) were infected, with L3 larvae of Litomosoides carinii and Dipetalonema viteae. Eighty days after infection the number of microfilariae (L1 larvae) was determined by smears from the peripheral venous blood. It was found that there were 48 and 69 X 10(3) microfilariae per ml blood. The hosts were killed and the eyes (conjunctiva, cornea, uvea, posterior part of the globe, optic nerve) as well as other organs (skin, brain, liver, heart and skeletal muscles, kidney, diaphragm and lung) were embedded for electron microscopic studies. Eight of the infected rodents, which are the specific hosts for these filariae, had been treated before the dissection with metrifonate (3 X 100 mg/kg) or diethylcarbamazine (3 X 250 mg/kg). These dosages led to the disappearance of microfilariae from the peripheral venous blood. In untreated controls microfilariae were found in the vessels of the chorioidea and retina, whereas after therapy there was no trace of these larvae in the eye. However, in the capillaries and in the interstitial space of other organs numerous degenerating microfilariae were observed. Furthermore, some larvae were seen intracellularly in liver and muscles. These intracellular stages had fewer or even no lesions compared to the extracellular ones, suggesting that they might escape the activity of the drugs. It is unknown whether similar phenomena occur in worms pathogenic to man. These laboratory models using the filariae of rodents (D. viteae with unsheathed and L. carinii with sheathed microfilariae) are very helpful for studying the pathogenic effects in eyes caused by microfilariae which circulate in the blood stream (Loa, Wuchereria).(ABSTRACT TRUNCATED AT 250 WORDS)