A parasitological study was undertaken to determine the health status of 15 mouse and 10 rat colonies bred in 18 Brazilian laboratory animal houses maintained under different sanitary barrier conditions which supply animals for teaching, research purposes and manufacture of biological products for medical or veterinary use. Parasitological methods were used for diagnosis of mites, lices, helminthes and protozoan parasites. A questionnaire was answered by institutions with the intention to obtain information about the existence of barriers against infections and of regular sanitary monitoring program of their colonies. The questionnaire data show that the majority of the animal houses investigated do not possess an efficient sanitary barrier system able to keep animals under controlled health sanitary conditions. Ecto and endoparasite infections are widespread in the colonies and multiple infections were common in animals from most facilities investigated. The prevalences of parasites detected among the mouse and rat colonies of the laboratory animal houses investigated were: Myocoptes musculinus (46.6%), Myobia musculi (26.6%), Radfordia ensifera (13.3%), Syphacia obvelata (86.6%), Aspiculuris tetraptera (60.0%), Hymenolepis nana (53.3%), Spironucleus muris (80.0%), Tritrichomonas muris (80.0%), Giardia muris (66.0%), Entamoeba muris (20.0%), Eimeria sp. (13.3%), Hexamastix muris (26.6%), Poliplax spinulosa (30.0%), Poliplax serrata (10.0%), Radfordia ensifera (30.0%), Syphacia muris (80.0%), Hymenolepis nana (40.0%), Trichosomoides crassicauda (55.5%), Spironucleus muris (90.0%), Tritrichomonas muris (80.0%), Giardia muris (60.0%), Entamoeba muris (80.0%), Eimeria sp. (60.0%) acid Hexamastix muris (60.0%).
