Dr Dewan SIbartie
Dermatophilosis in humans-A first suspected case in Mauritius
Dr Dewan Sibartie, Veterinary Consultant
Dermatophilosis (Streptothricosis) also called “rain rot” in cattle is an acute or chronic bacterial infection of the epidermis affecting various species of animals and occasionally humans. It is caused by Dermatophilus congolensis, an aerobic actinomycete (facultatively anaerobic) bacterium. Distributed worldwide, but prevailing mainly in tropical areas and humid environments, it is responsible for significant economic losses in livestock. Clinically, the disease is characterized by an exudative dermatitis with heavy scab formation accompanied by poor production and occasional deaths. It is spread by contact with infected animals and via contaminated environmental objects. Infestation with ectoparasites such as ticks break the integrity of the skin and favours transmission amongst animals.
Dermatophilosis is frequently diagnosed in cattle in Mauritius. In 2023, following the heavy rains observed in January, several cattle farms have been affected. Recently, one cattle breeder from the North of the island called at Maurivet Ltd. to “buy” antibiotics. He showed the Sales Assistant some pictures and a video of his affected cows. At the same time, the Sales Assistant noticed prominent skin lesions on the farmer himself and therefore referred the case to me.
Based on the history of the disease condition on his farm along with the video showing crusty and desquamated skin lesions around the eye and muzzle of the cattle, (see photos), a diagnosis of dermatophilosis was obvious. The farmer was given the appropriate antibiotics and advised accordingly regarding treatment and future preventive measures.
With the agreement of the farmer, I physically examined the lesions on his skin. The neck region was discoloured and covered with pustules and crusts (see photos). Desquamated lesions with elevated edges were also present. Similar lesions were seen on the right arm and the right foot. According to the farmer, the lesions were not painful nor did he feel any itch in the affected parts of the skin. Application of anti-fungal cream prescribed by his dermatologist had not produced any significant beneficial effect. He informed that he was the main person in daily contact with the animals and he always handled his cows with his right arm and foot, hence the location of the lesions. Based on the history of the ailment in the cows, and the skin lesions on the body of the farmer, a diagnosis of dermatophilosis was not difficult. The demonstration on a Gram or Giemsa stain of the skin smears, of typical branching filamentous bacterium, provides a confirmatory evidence of the infection. Isolation and morphological identification of cultures on blood agar can be carried out in Mauritius for further evidence. Detailed biochemical/nuclear tests are more specific but can be useful only for research purposes.
The attending dermatologist was contacted and advised accordingly.
Dermatophilosis is very rarely reported in humans. Although the transmission mechanism is not clearly known, mechanical transfer from infected animals is commonly accepted as the main route of transmission. Previous skin lesions also seem to facilitate transmission of the infective agent. In the above case which is the first suspected case in Mauritius, it is unquestionable that the farmer contracted it from his cattle.
Just as is the case in other countries, it is likely that many human cases of dermatophilosis pass unnoticed in Mauritius. It is suggested that skin infections especially arising from existent skin lesions be further investigated in farmers and those closely associated with domestic animals such as sheep, goats and horses and other people in contact with wild animals such as cats, buffaloes and deer.
Acknowledgement: I am thankful to the Sales Assistant of Maurivet Ltd., Mrs Joanna Ghanseeram for referring the case to me.