Chlorellosis: An emerging algal disease of Animals and Humans

Chlorellosis, an emerging opportunistic algal disease, is reported from Australia, Brazil, India, Mexico, Sudan and USA. The disease is caused by Chlorella, a ubiquitous alga, which has been recovered from diverse natural substrates including water. Sporadic cases of cutaneous and systemic chlorellosis are recorded in humans and many species of animals. Most cases in cattle are accidentally detected during meat inspection in abattoirs. The incidence of disease is usually high in areas of wetlands with poor sanitation. The source of infection is exogenous and immunosuppression, skin trauma and heavy environmental exposure are considered as the predisposing factors. The exact mode of transmission is not yet clearly established. Disseminated disease occurs in severely immunocompromised individuals. Microscopic examination of wet mounts of wound exudates or touch smears from infected tissues may help to observe bright green pigment granules of Chlorella. However, transmission electron microscopy can support the diagnosis of disease. Currently, molecular tools have been applied to confirm Chlorella infection. The surgical excision of affected part remains the only choice of disease management. Removal of animals from the affected area, avoiding barbed wire injury, algicidal treatment of water and immediate attention to superficial wound may be effective strategies to control chlorellosis. Further studies on the ecology, pathogenesis, diagnosis, epidemiology, and chemotherapy are needed to get a better insight of this unusual emerging pseudofungal disease. It is recommended that the efficacy of “PHOL” and “Narayan” stain to undertake the detailed microscopic morphology of Chlorella isolates and Pal sunflower seed medium for the isolation of Chlorella from clinical and environmental material should be investigated.