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One of the scope of DBVPG Collection is the isolation, identification and genotype-specific PCR characterization of Prototheca spp. strains from milk and barn-surrounding environmental samples (bedding, feces, drinking or washing water, swabs) of dairy herds.

The genus Prototheca includes unicellular achlorophyllous yeast-like microalgae (taxonomically related to the genus Chlorella)exhibiting asexual reproduction by multiple splitting and forming from 2 to 16 endosporulating cells. Conventionally, the genus Prototheca encompasses five species: P. stagnoraP. ulmeaP. wickerhamiiP. zopfii and P. blaschkeae. A sixth species, P. moriformis, is not currently accepted because of its biochemical/genetic resemblance with P. zopfii and of its high intraspecific heterogeneity. Besides, on the basis of its biochemical, serological and 18S-rDNA sequencing data, P. zopfii has been recently differentiated into two genotypes: genotype 1 and genotype 2.

Prototheca spp. strains are often associated with wet areas containing decaying manure and plant matter. They can also be found in flowing water, standing water, water tanks, water runoff from silage, well water, milking parlour wash water, manure, teat dip containers, milking machine liners, teat end swabs and feed troughs. Strains of Prototheca spp. have been isolated both from environmental sites (e.g. soils, waters, faeces of rats) on dairies having cows infected with this microalga, indicating that Prototheca spp. cells are widely dispersed in dairy environments. Human protothecosis are generally associated with P. wickerhamii. On the contrary, bovine mastitis (the most common protothecosis in animals) is caused by P. zopfii genotype 2 and by P. blaschkeae.

Cattle udder infections caused by Prototheca spp. strains have been linked to the constant contact of the mammary gland with water sources on the dairy. All stages of lactation appear to be equally susceptible to new infections including dry cows. Mammary gland infections caused by Prototheca strains are rarely observed with clinical signs. Non-clinical outbreaks are frequently characterized by the secretion of milk characterized by a normal or only slightly increased number of somatic cell count. In some cases a reduced milk production is sometime observed in cows with sub-clinical infections.

Bovine mastitis caused by Prototheca spp. strains is an increasing global phenomenon and the efficacy of therapies with antimicrobial drugs is still controversial.



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