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Achlorophyllous, yeast-like microalgae of the genus Prototheca (P.) are the only known plants, able to cause infections in humans and animals. Until now five different species have been described. One of them –Prototheca zopfii genotype 2– was identified to be responsible for inflammation of the mammary gland in dairy cows as well as for the sporadically occurring prototheca infection in dogs. In the case of affected dogs the clinical signs are often associated with hemorrhagic, therapy-resistant enterocolitis, which later, in the generalized manifestation of the pathogens, occur in combination with ocular and central nervous disorders.
Due to these observations, the present study was focused on the following objectives: (1) to develop an ELISA test system in order to detect prototheca-specific antibodies of the genus Prototheca zopfii genotype 2 in dog serum and based on this (2) to investigate the prevalence of Prototheca infection in a large dog population. For this purpose 363 dogs, divided into three groups, were culturally and serologically tested. The first group (n=236) included healthy dogs, acutely ill and orthopedic ill patients as well as dogs with proven benign tumors. The second group (n=65) consisted of dogs with gastrointestinal symptoms and the third group (n=62) involved dogs that had chronic, malign or immune-mediated diseases without any gastrointestinal signs.
In addition an ELISA test system could be established that succeeded in demonstrating species-specific P. zopfii genotype 2 antibodies in enteritic ill patients suffering from protothecosis. With a specificity and sensitivity of 100 % the developed ELISA test indicated a very good diagnostic suitability. Within the scope of this study, the canine protothecosis was confirmed culturally and serologically in 2 cases (case FU 1 and FU 2) of the investigated dog population. This corresponds to a prevalence of 3.1 % in the enteritic dogs from group 2. In dogs from group 1 and 3 no Prototheca species were found in the feces or in the blood serum. The proven prevalence of 3.1 % of the canine protothecosis in enteritic dogs suggests that the Prototheca infection should be considered as one differential diagnosis of dogs showing clinical signs of gastrointestinal disease. Due to intermittent pathogen shedding in the feces and thereby the possible danger of false negative results, the established serological test can be very useful. Compared to previously described methods, the indirect test system, depicted in this study, enables a fast and secure identification of Prototheca antibodies in blood serum and therefore provides a promising tool for Prototheca diagnostic in the clinical practice.