ISSN 2398-2993      

Mycoplasma wenyonii


Ben Strugnell

James Breen

Synonym(s): M. wenyonii, Eperythrozoon wenyonii

Podcast: Mycoplasma wenyonii




  • Class: Mollicutes.
  • Order: Mycoplasmatales.
  • Family: Mycoplasmataceae.
  • Genus: Mycoplasma.
  • Species: wenyonii.
  • Formerly known as Eperythrozoon wenyonii.
  • Other clinically significant members of this group include:
    •  Mycoplasma suis which affects pigs.
    • Mycoplasma haemofelis which affects cats.
    • Although thought to be host-specific, some species have been reported to be zoonotic.


  • Gk: myco - fungus; plasma - form; mycoplasma - a fungus form.

Clinical Effects

Pathological effects

  • Hindlimb edema (hindlimbs 'fill up' with pitting edema to mid-tibia, although affected cows not usually lame) :
    • Exactly how this blood borne parasite with a tropism for the erythrocyte membrane causes or contributes to clinical signs of hindlimb and udder edema is not yet understood, research is ongoing.
    • Examination of biopsy samples, from edematous skin, has indicated that the edema may be caused by vasculitis, possibly an Arthus-type reaction with deposition of immune complexes in the vascular endothelium.
    • In some cases, there has been an association with recent vaccination, raising the possibility of immune stimulation by adjuvants and precipitation of immune-mediated pathology.
  • Pyrexia may result in milk drop, malaise and inappetence.
  • Painful, swollen udders in dairy cows. 
  • Milk drop Investigating milk drop in the herd Investigating milk drop in the individual cow: clots may be seen in the milk Mastitis: unusual forms.
  • Lymphadenopathy: prefemoral lymph nodes are enlarged and easily palpable.
  • Scrotal edema (could have significant effects on male fertility).
  • Diarrhea.
  • Depression.
  • Anemia: a case has been reported (Gladden 2015) of a cow presenting with post-calving vaginal bleeding, which on investigation was found to have a regenerative anemia and tested positive for M. wenyonii. This animal had suffered milk drop but had no hindlimb edema. The authors concluded that in this case the anemia was associated with M. wenyonii.
Clinical signs in dairy cows gradually resolve but full recovery may take 10 days or longer.


  • No vaccine available.


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Further Reading


Refereed Papers

  • Recent references from PubMed and VetMedResource.
  • Schambow et al (2021) Apparent prevalence of Mycoplasma wenyonii, Candidatus Mycoplasma haemobos and bovine leukemia virus in Winsconsin and Michigan dairy cattle herds. JDS Comms 2 (2), 61-66 SciDirect.
  • Ade J, Niethammer F, Schade B et al (2018) Quantitative analysis of Mycoplasma wenyonii and 'Candidatus Mycoplasma haemobos' infections in cattle using novel gapN-based realtime PCR assays. Vet Microbiol 220, 1-6 PubMed.
  • McFadden A, Ha H J, Donald J J et al (2016) Investigation of bovine haemoplasmas and their association with anaemia in New Zealand cattle. N Z Vet J 64 (1), 65-68 PubMed.
  • Gladden N (2015) A case report of Mycoplasma wenyonii associated immune-mediated haemolytic anaemia in a dairy cow. Cattle Pract 23 (2), 202. 
  • Gladden N (2015) A case report of Mycoplasma wenyonii associated immune-mediated haemolytic anaemia in a dairy cow. Cattle practice 23 (2), 202.
  • Hoelzle K, Winkler M, Kramer M M et al (2011) Detection of Candidatus Mycoplasma haemobos in cattle with anaemia. Vet J 187, 408-410 PubMed.
  • Strugnell B W, McAuliffe L, Longmire K & Ellis-Iverson J (2010) Mycoplasma wenyonii associated with clinical signs in milking dairy cows after herd-wide bluetongue vaccination. Cattle Pract 19, 75-81.
  • Yuan C L, Liang A B, Yao C B et al (2009) Prevalence of Mycoplasma suis (Eperythrozoon suis) infection in swine and swine-farm workers in Shanghai, China. Am J Vet Res 70, 890-894 PubMed.
  • dos Santosi A P, dose Santos R P, Biondo A W et al (2008) Hemoplasma infection in HIV-positive patient, Brazil. Emerg Infect Dis 14, 1922-1924 PubMed.
  • Scott R (2008) Distal hind limb and udder oedema of dairy cattle associated with an unidentified haemotrophic bacterium with microscopic characteristics of Mycoplasma (formerly Eperythrozoon) wenyonii. Cattle Pract 16, 50-53.
  • McAuliffe L, Lawes J, Bell S et al (2006) The detection of Mycoplasma (formerly Eperythrozoon) wenyonii by 16S rDNA PCR and denaturing gradient gel electrophoresis. Vet Microbiol 117, 292-296 PubMed.
  • Hofmann-Lehmann R, Meli M L, Dreher U M et al (2004) Concurrent infections with vector-borne pathogens associated with fatal hemolytic anemia in a cattle herd in Switzerland. J Clin Microbiol 42, 3775-3780 PubMed.
  • Welles E G, Tyler J W & Wolfe D F (1995a) Haematologic and semen quality changes in bulls with experimental Eperythrozoon infection. Theriogenology 43, 427-437 PubMed.
  • Welles E G, Tyler J W & Wolfe D F & Moore A (1995b) Eperythrozoon infection in young bulls with scrotal and hindlimb edema, a herd outbreak. Theriogenology 43, 557-567 PubMed.
  • Montes A J, Wolfe D F, Welles E G, Tyler J W & Tepe E (1994) Infertility associated with Eperythrozoon wenyonii infection in a bull. JAVMA 204, 261-263 PubMed.
  • Kawaku S, Nakamura Y, Kamio T et al (1990) Enzyme-linked immunosorbent assay for detection of antibodies to Eperythrozoon wenyonii in cattle. Jap J Vet Sci 52, 1297-1300.
  • Smith J A, Thrall M A, Smith J L et al (1990) Eperythrozoon wenyonii infection in dairy cattle. JAVMA 196, 1244-1250 PubMed.
  • Quinlan J F (1985) Suspected Eperythrozoonosis in dairy cows. Ir Vet J 39, 27.
  • Sutton R H, Charleston, W A G & Collins G H (1977) Eperythrozoon wenyonii – a blood parasite of cattle. A first report in New Zealand. NZ
    Vet J 25, 8-9.
  • Poole D B R, Cutler R S, Kelly W R & Collins J D (1976) Eperythrozoon wenyoni anaemia in cattle. Vet Rec 99, 481.
  • Kreifer J P & Ristic M (1963) Morphologic, antigenic and pathogenic characteristics of Eperythrozoon ovis and Eperythrozoon wenyoni. Am J Vet Res 24, 488-500.

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