New strain of the parasite responsible for dourine identified by researchers

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Giemsa-stained T. equiperdum isolated from the urethral tract of the dourine-infected stallion. a and b (1K1N) show the single form of T. equiperdum. c (2K1N) and d (2K2N) show the dividing form of T. equiperdum. Arrows show the nucleus and arrowheads kinetoplast.
Giemsa-stained T. equiperdum isolated from the urethral tract of the dourine-infected stallion. a and b (1K1N) show the single form of T. equiperdum. c (2K1N) and d (2K2N) show the dividing form of T. equiperdum. Arrows show the nucleus and arrowheads kinetoplast.

Researchers have identified a new strain of the parasitic protozoan organism responsible for the sexually transmitted disease, dourine, in horses.

The case was diagnosed in a stallion in Mongolia.

Dourine, also known as covering sickness, is caused by Trypanosoma equiperdum, which belongs to an important genus of parasitic protozoa. It is the only member of the Trypanosoma genus that is spread through sexual intercourse rather than insect vectors.

Dourine is a notifiable disease in the European Union.

Noboru Inoue and his colleagues, writing in Parasites & Vectors, said the organisms, known as trypanosomes, were isolated from the urethral tract of a stallion suspected to have dourine.

They were cultivated under laboratory conditions and subjected to genetic analysis, which indicated it was a new strain.

“We concluded that our isolated trypanosome was the first confirmed case of T. equiperdum in Mongolia and named it “T. equiperdum IVM-t1”.

The study team noted that many of the T. equiperdum strains were first isolated over 50 years ago, and it was hypothesized that some of the isolates were actually misclassified T. evansi strains.

Some new T. equiperdum strains were recently isolated in Italy and Ethiopia from horses with suspected dourine infections, the researchers noted.

“However, these T. equiperdum strains were not directly isolated from the genital mucosa – the primary site of infectious lesions of T. equiperdum. Instead, they were isolated from udder secretion samples or jugular venous blood.

“Thus, new T. equiperdum strains that are directly isolated from the infectious lesions of horses with clinically- and parasitologically-confirmed dourine have long been needed for further studies on T. equiperdum and dourine.”

Previous reports have shown that the prevalence in horses of trypanosomosis – that is, disease caused by protozoan pathogens of the genus Trypanosoma – was 6–8 % in Mongolia and 16.8% in Kazakhstan.

“However, these reports did not identify the causative species because it is very difficult to distinguish T. equiperdum from T. evansi using serological diagnostic techniques.”

The researchers said their ongoing epidemiological research suggested a high prevalence of trypanosomoses in horses in Mongolia.

Inoue was joined in the research by Keisuke Suganuma, Sandagdorj Narantsatsral, Banzragch Battur, Shino Yamasaki, Davaajav Otgonsuren, Simon Peter Musinguzi, Batdorj Davaasuren and Badgar Battsetseg.

Isolation, cultivation and molecular characterization of a new Trypanosoma equiperdum strain in Mongolia
Keisuke Suganuma, Sandagdorj Narantsatsral, Banzragch Battur, Shino Yamasaki, Davaajav Otgonsuren, Simon Peter Musinguzi, Batdorj Davaasuren, Badgar Battsetseg and Noboru Inoue

The study, published under a Creative Commons License, can be read here

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