II. Lymphocytic Choriomeningitis (LCM)
III. Hamster Polyomavirus
A. Etiology: Sendai virus and PVM are RNA viruses of the paramyxovirus group. Sendai virus is a parainfluenza virus type 1 and PVM is a pneumovirus that is serologically distinct from Sendai virus. Incidence of infection with these viruses is high although clinical disease is rarely observed.
B. Clinical Signs: Infection are asymptomatic.
C. Pathology: No lesions are observed on gross or histologic tissue examinations.
D. Diagnosis: Diagnosis is based on identification of antibody by serological testing, usually by ELISA.
E. Control: Hamsters should not be housed in the same room as mice, rats, or guinea pigs. In mice, propagation of the viruses depends on continual introduction of susceptible animals. Virus is eliminated when breeding or introduction of naive animals is stopped for at least 60 days. This technique should work in hamsters.
II. Lymphocytic Choriomeningitis Virus (LCM)
A. Etiology: LCM is a RNA virus of the arenavirus group. Incidence of infection and spontaneous disease is rare. Most reported human cases have been associated with infected hamsters.
B. Transmission: In utero or perinatal infections (within 1 day post-partum) may produce a subclinical persistent infection or a chronic, progressive wasting disease. The virus is intermittently shed in urine and saliva with the concomitant production of antibody. Approximately half the infected hamsters will clear the infection. If infected as young adults, antibody production and persistent viruria and viremia continue for up to 6 months. The natural reservoir for LCM is the wild rodent population. Transmission occurs via urine and saliva, traumatized skin, conjunctiva, respiratory passages, or congenital contamination. In research involving hamsters, a common route of infection is the transplantation of LCM-contaminated tumors.
C. Clinical Signs: Usually there are no clinical signs. Wasting syndrome and death may occur in hamsters with persistent infections. Signs can include convulsions, decreased growth, and inactivity. Decreased reproduction has been reported in chronically infected females.
D. Pathology: Gross lesions vary and if present, may include splenomegaly, swollen or shrunken, pitted kidneys, lymphadenopathy, hepatomegaly. Gross lesions alone are not diagnostic. Microscopic lesions include lymphocytic meningitis, chronic glomerulonephropathy, widespread vasculitis, and marked lymphocytic infiltration of the viscera.
E. Diagnosis: Diagnosis is based partly upon the lymphocytic infiltration of the meninges, choroid plexuses, and of submeningeal and subchoroid perivascular spaces. ELISA tests are used to detect serum antibodies to LCM. PCR of fresh hamster tissue or transplantable cells/fluids can be used to diagnose persistent or acute infections. Injection of hamster blood or tissues into LCM-free mice will produce clinical signs and antibody titers in 2 weeks.
F. Control: All hamsters at risk for infection from horizontal and vertical transmission should be euthanatized and evaluated for diagnostic examinations. Major efforts to disinfect cages and equipment once the hamsters have been eliminated should be immediately employed. The wild rodent population should be controlled.
Public Health Significance: People are susceptible to LCM virus, and experience flu-like symptoms and occasional nonsuppurative meningitis. Past reports of zoonosis have linked human infections to exposure to infected pet hamsters.
Hamster polyomavirus is a DNA oncogenic virus
that induces 2 neoplastic syndromes in hamsters depending on the age of
the animal at the time of infection. Young hamsters develop a multicentric
lymphoma involving mesenteric lymph nodes and abdominal viscera. Virus
is shed in urine, and other naive young hamsters can become infected and
develop lymphoma. This syndrome has been described as transmissible
lymphoma when the viral disease occurs in breeding colonies. The
other neoplastic syndrome occurs in adult hamsters, and viral infection
results in skin neoplasms described as trichoepitheliomas. Virus is shed
from infected epithelial cells. The viral syndromes are uncommon, and control
measures are based on depopulation and restocking with virus-free hamsters.
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