Trichomonas

Trichomonas is a genus of single-celled, flagellated protozoa in the class Trichomonadea. Members are anaerobic or microaerophilic and generally inhabit mucous surfaces of humans and animals. They belong to the phylum Parabasalia and are characterized by a nucleus, an undulating membrane, and multiple flagella; energy is produced by hydrogenosomes rather than mitochondria. Most species reproduce asexually by binary fission and do not form cysts, which influences transmission.

The best-known species is Trichomonas vaginalis, the causative agent of trichomoniasis in humans. It is primarily spread through sexual contact; many infections are asymptomatic. In women, infection may cause vaginitis with discharge, itching, and irritation; in men, urethritis or epididymitis can occur. Diagnosis relies on a combination of nucleic acid amplification tests (NAATs), wet mount microscopy, and culture. Treatments include metronidazole or tinidazole; patients should avoid alcohol during and after treatment with nitroimidazoles, and sexual partners should be treated.

Other Trichomonas species have different hosts and pathogenicity. Trichomonas tenax inhabits the human oral cavity and is usually nonpathogenic, occasionally linked to dental disease in vulnerable individuals. Trichomonas hominis, found in the human intestine, is typically not disease-causing. Trichomonas gallinae infects birds, notably pigeons and doves, causing avian trichomoniasis (“canker”) and significant morbidity in affected flocks.

Trichomonas species are of interest in parasitology for their diverse host range, lack of cyst formation, and reliance on hydrogenosomes. Control focuses on proper diagnosis, treatment of human cases, partner notification, and, in animals, management and prevention of transmission.