The Coxsackie viruses comprise a large subgroup of the enteroviruses. They produce a variety of illnesses in humans, including aseptic meningitis, herpangina, pleurodynia, hand, foot and mouth disease, myo- and pericarditis, common cold, and possibly diabetes, Coxsackie viruses have been divided into 2 groups; A and B, having different pathogenic potentials for mice. Coxsackie B viruses are the most commonly identified causative agents of viral heart disease in humans.
Properties of the Viruses
Coxsackie viruses are typical enteroviruses, with a diameter of 28nm.
Animal susceptibility and Growth of Virus
Coxsackie viruses are highly infective for newborn mice. Certain strains (B1-B6, A7, 9, 16) also grow in monkey kidney cell culture. Some group N strains grow in human amnion and human embryonic lung fibroblast cells. Chimpanzees and cynomolgus monkeys can be infected sub-clinically; virus appears in the blood and throat for short periods and is excreted in the feces for 2-5 weeks. Type A14 produces poliomyelitis-like lesions in adult mice and in monkeys, but in suckling mice this type produces only myositis, Type A7 strains produces paralysis and severe central nervous system lesions in monkeys.
Group A viruses produce widespread myositis in the skeletal muscles of newborn mice, resulting in flaccid paralysis without other observable lesions. Group B viruses may produce focal myositis, encephalitis and most typically, necrotizing steatites involving mainly fetal fat lobules. The genetic makeup of inbred strains determines their susceptibility to Coxsackie B viruses. Some B strains also produce pancreatitis, myocarditis, endocarditis and hepatitis in both suckling and adult mice. Corticosteroids may enhance the susceptibility of older mice to infection of the pancreas. Normal adult mice tolerate infections with group B Coxsackie viruses. However, severely malnourished or immuno-deficient mice have greatly enhanced susceptibility.
At least 32 different immunologic types of Coxsackie viruses are not recognized; 26 are listed as group A and 6 as group B types.
Coxsackie and ECHO viruses posses relatively high resistance. They survive for a long period of time in a frozen state at -70 degrees Celsius. In glycerin and horse serum at room temperature they persist for 70 days. In a refrigerator they survive for more than a year. The Coxsackie viruses resemble the poliomyelitis viruses in that they are resistant to various concentrations of hydrogen ions. They survive at pH 2.3-9.4 for 24 hours and at pH 4.0-8.0 for 7 days. They are resistant to antibiotics, 70 degrees ethyl alcohol, and 5% Lysol solutions but are extremely sensitive to solutions of hydrochloric acid and formaldehyde. A temperature of 50-55 degrees Celsius kills the viruses in 30 minutes.
Pathogenesis and pathology
Virus has been recovered from the blood in the early stages of natural infection in humans and of experimental infection in Chimpanzees. Virus is also found in the throat for a few days early in the infection and in the stools for up to 5-6 weeks. The distribution of virus is similar to that found with the other enteroviruses. Group B Coxsackie viruses may cause acute fatal encephalomyocarditis in infants. This appears to be a generalized systemic disease with virus replication and lesions in the central nervous system, heart muscle, and other organs.