Investigations into the biology of three ?phycomycotic? agents pathogenic for horses in Australia

Abstract

Although 'phycomycosis' is a common disease of horses in northern Australia little is known about the causative fungi. In this paper the laboratory methods for diagnosis are described. These revealed 38 cases caused by Pythium sp. (Hyphomyces destruens), 6 cases caused by Basidiobolus haptosporus and 2 caused by Conidiobolus coronatus. Laboratory studies on the chemotatic behaviour of zoospores of Pythium sp. showed that they were strongly attracted to both animal hairs and plant tissue. Because of this behaviour a simple baiting method using human hair was used to trap the fungus from water samples taken from different locations near Townsville, Queensland. B. haptosporus was isolated by indirect culture from the faeces of 5 bearded dragon lizards (Amphibolurus barbatus) captured near a small creek near Brisbane. By combining previously published information with data obtained in the present study, ecological life-cycles for Pythium sp., B. haptosporus and C. coronatus are proposed. They include mechanisms whereby horses may become infected.

Epidemiologia da pitiose equina na Região Sul do Rio Grande do Sul

“…Esta temperatura ambiente é, aparentemente, suϐiciente para que o agente produza zoósporos infectantes que iniciam a doença após penetrarem na pele do animal (Miller 1983, Mendoza et al 1996. Por outro lado, deve ser considerado que P. insidiosum é um organismo aquático e as formas infectantes (zoósporos) se desenvolvem dentro de águas paradas como açudes, banhados, canais de irrigação e campos alagados, no entanto a temperatura ideal dessas águas para o desenvolvimento da forma infectante do agente é desconhecida.…”

“…Nestes ambientes P. insidiosum realiza seu ciclo de reprodução formando zoósporos infectantes, que ao serem liberados nas águas são atraídos por quimiotaxia para tecidos daniϐicados, onde se ϐixam e emitem tubos germinativos dando início a enfermidade (Mendoza et al 1996, Miller 1983. Comumente, observa-se que os animais afetados permanecem por longos períodos em contato com águas estagnadas (Chafϐin et al 1995).…”

The Comparative Pathology of Equine Cutaneous Phycomycosis

“…16 The fungus B. ranarum first was isolated from a horse in Indone~ia'~ and later B. haptosporus was isolated from horses in A~stra1ia.l~ It now is believed that all pathogenic isolates of Basidiobolus spp in mammals are B. haptosporus. 15 Conidiobolomycosis occurs almost exclusively in the nasal region and appears clinically as single or multiple firm, usually ulcerated, nodules and granulomas.…”

Pitiose em equinos

“…Reproduz-se de forma sexuada, dando origem aos zoosporângios (MILLER, 1983;MENDOZA HERNANDEZ e AJELLO, 1993;BIAVA et al, 2007). Os zoósporos livres na água tem um forte tropismo por pêlos e por tecidos animais e vegetais, onde se encistam e secretam um material amorfo que os BROMERSCHENKEL, I. e FIGUEIRÓ, G.M.…”