Porcine parvovirus
| Porcine parvovirus | |
|---|---|
| Virus classification | |
| Group: | Group II (ssDNA) |
| Family: | Parvoviridae |
| Subfamily: | Parvovirinae |
| Genus: | Protoparvovirus |
| Species: | Porcine parvovirus |
Porcine parvovirus (PPV) causes reproductive failure of swine characterized by embryonic and fetal infection and death, usually in the absence of outward maternal clinical signs. The disease develops mainly when seronegative dams are exposed oronasally to the virus anytime during about the first half of gestation, and conceptuses are subsequently infected transplacentally before they become immunocompetent. There is no definitive evidence that infection of swine other than during gestation is of any clinical or economic significance. The virus is ubiquitous among swine throughout the world and is enzootic in most herds that have been tested. Diagnostic surveys have indicated that PPV is the major infectious cause of embryonic and fetal death. In addition to its direct causal role in reproductive failure, PPV can potentiate the effects of porcine circovirus type II (PCV2) infection in the clinical course of postweaning multisystemic wasting syndrome (PMWS).
Acute infection of postnatal pigs, including pregnant dams that subsequently develop reproductive failure, is usually subclinical. However, in young pigs and probably in older breeding stock as well, the virus replicates extensively and is found in many tissues and organs with a high mitotic index. Viral antigen is especially concentrated in lymphoid tissues (Fig. 3A, B). Many pigs, irrespective of age or sex, have a transient, usually mild, leukopenia sometime within 10 days after initial exposure to the virus. PPV and other structurally similar viruses have been identified in the feces of pigs with diarrhea. However, there is no experimental evidence to suggest that PPV either replicates extensively in the intestinal crypt epithelium or causes enteric disease as do parvoviruses of several other species. PPV also has been isolated from pigs with lesions described as vesiclelike. The causal role of PPV in such lesions has not been clearly defined.
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