Ectromelia virus

Prevalence
Rare.
DNA virus; Poxviridae.
 
Diagnosis
Clinical signs, serology (false positive if experimental design involves dosing vaccinia virus), histology (intracytoplasmic inclusion bodies), PCR on skin lesions.
 
Disease
In susceptible strains, high mortality with or without clinical signs. At necropsy there is liver and lymphoid tissue necrosis. In animals which do not succumb to Peracute death the cklinical signs are ruffled fur, hunched posture, oedema of face and legs, conjunctivitis, cutaneous pustules, ulceration of muzzle, ears, limbs, tails and partial amputation of limbs and tail.
 
Strains
Resistant strains include C57Bl/6, C57BL/10 and AKR (carrier status can exist in these strains)Susceptible strains include A, CBA, C3H, BALB/c, DBA/2. 
 
Screening
Routine monitoring is essential of animals and murine0-derived biological products.
 
Transmission
Direct contact or fomites. 
 
Duration
Lesions appear 7-10 days post infection, virus is shed for 3 weeks.
 
Durability
Virus may exist in skin lesions for 3-4 months post infection.
 
Significance
In susceptible strains, high mortalities will affect research. In resistant animals there is evidence that Ectromelia virus may modify phagocytic cell behaviour. Muine biological products may be infected resulting in spread of the infection. 
 
Control
Pathogen exclusion by regular monitoring of mice and murine-derived biological products. Rederivation by hysterectomy or embryp transfer is the gold standard for disease eradication. 
 
Reading
  • Infectious Diseases of Mice and Rats National Research Council 1991.
  • Pathology of Laboratory Rodents and Rabbits, 3rd Edn., Dean H Percy & Stephen W Barthold, 2007.
  • University of Missouri, Research Animal Diagnostic Laboratory website, http://www.radil.missouri.edu