Parvoviruses are single stranded DNA viruses with an average genome size of 5 kbp. Parvoviruses are among some of the smallest viruses found in nature (hence the name, from Latin parvus meaning small). Many types of mammalian species have a strain of parvovirus associated with them. Parvoviruses tend to be specific about the taxon of animal they will infect, but this is a somewhat flexible characteristic. Thus, all strains of canine parvovirus will affect dogs, wolves, and foxes, but only some of them will infect cats.
Among the mammalian species in which Parvovirus causes significant infections are dogs, cats and pigs. In dogs the disease is canine parvovirus, in cats it is feline panleukopenia or more commonly called feline distemper (not related to canine distemper) , and in pigs it is SMEDI (an acronym of stillbirth, mummification, embryonic death, and infertility).
General - Canine parvovirus (CPV) is a contagious virus affecting dogs. The disease is highly infectious and is spread from dog to dog by physical contact and contact with feces. It can be especially severe in puppies. CPV is a relatively new disease orginating in the 1970's. It is similar to feline distemper and the virus only differs from the feline parvovirus by two amino acids in the produced protein coat of the virus. Some think it may have been a mutation of the feline virus that produced the original canine variety but that has not been conclusively established.
Infection/prevention - Dogs become infected through oral contact with CPV in feces, infected soil, or fomites carrying the virus. Puppies are most susceptible due to immature immune systems. If the bitch is infected while pregnant, it can lead to abortions, birth defects and infertility. The disease however in dogs is more related to exposure after birth and up through 1 year of age. In these individuals it will attack either the heart or intenstine. Although most individuals recover, they may suffer perminant damage to these organs. Treatment of infected individuals with symptoms of gastroenteritis (lethargy, anorexia, fever, vomiting and diarrhea) are given supportive therapy (oral or IV electrolytes) but no cure is possible. The version that attacks the heart is no longer common as most bitchs are vaccinated and this type was usually associated with infection just prior to or after birth. Protection is via vaccination of the bitch and multiple vaccination of puppies.
General - Feline panleukopenia virus is the feline parvovirus that is closely related to canine parvovirus. The disease caused by this virus in cats is called panleukopenia or feline distemper (not related to canine distemper).
Infection/Prevention - Panleukopenia is primarily spread through contact with an infected cat's bodily fluids, feces, or fleas. The virus may also sometimes spread through contact with bedding, food dishes, or even by handlers of infected cats. The virus primarily attacks the lining of the gastrointestinal tract, causing internal ulceration and, ultimately, total sloughing of the intestinal epithelium. This results in profuse, usually bloody diarrhea, causing severe dehydration, malnutrition, anemia, and often death; mortality rate 60-90%. The virus causes a decrease in the cat's white blood cells, thus compromising its immune system. Typically, infection causes a decrease in WBC, hematocrit and platelet counts on a CBC. This is often key in diagnosing panleukopenia. Symptoms include depression, lethargy, loss of appetite, a high fever, vomiting, diarrhea, and loss of skin elasticity.
If a pregnant cat is exposed during pregnancy, the virus can cause cerebellar hypoplasia in her offspring. This is why administering modified live feline panleukopenia vaccine during pregnancy is discouraged. The Panleukopenia vaccination guidelines have changed over the years but current prevention guide lines are to vaccinate kittens and then booster at 3 year intervals. More frequent boosters have been associated with increased renal disease.
General - Porcine parvovirus (PPV) infection is a common cause of reproductive failure in breeding pigs throughout the world.
Infection/Prevention - The virus, PPV is present in most piggeries but careful isolation of the herd or establishment of a specific pathogen free herd can result in a PPV negative herd. The PPV induces reproductive failure when susceptible (non-immune) gilts and sows are infected during pregnancy. This is the only time the virus causes disease. Infection in the pig occurs following ingestion or inhalation of the virus. The PPV then circulates in the bloodstream, and in the pregnant pig crosses the placenta and infects the developing embryos and foetuses. Following natural infection, active immunity develops that probably lasts for the life of the pig. If active immunity occurs before pregnancy then the developing piglets are not affected. At birth the piglets receive maternal immunity in the colostrum from the sow and this maternal immunity lasts for up to 20 weeks of age. The greater the level of active immunity in the sow, the more maternal immunity that she passes onto her piglets. Thereafter, natural infection with PPV can occur.
A pig recently infected with PPV excretes the virus in saliva and faeces for about two weeks following infection. The virus is very hardy and can survive for up to 100 days outside the pig. Of importance to the disease free herd is that the boar can also be infected with PPV but does not produce any clinical signs. He can excrete the virus following infection into the semen and can pass it onto sows and gilts at mating or artificial insemination.
The disease caused by PPV in pigs is often refered to as a SMEDI (an acronym of stillbirth, mummification, embryonic death, and infertility). If infection occurs at days 0-30 of pregnancy, embryonic mortality can occur, resulting in returns to service and decreased litter size. The most obvious feature following infection at 30-70 days of pregnancy is the birth of mummified piglets. Mummification is the process of sterile digestion of the tissues of the piglets that die in the uterus after the skeleton has started to solidify. PPV-infection is also associated with stillbirths and weak born pigs if infection occurs in the later stages of pregnancy. Abortion can also be the result of PPV-infection, but is not a common clinical sign of this disease. Overall, PPV-infection decreases the number of pigs born per sow per year.
Prevention is either accomplished by having and maintaing a PPV head or vaccination. In a herd being vaccinated for the first time, all breeding pigs, boars, sows and gilts should receive two doses of vaccine four weeks apart. A booster dose of vaccine is given every six months. Alternatively in sows, the booster dose can be given at each weaning. Replacement gilts and boars require two doses of vaccine four weeks apart prior to mating, followed by the six monthly booster dose.