Picornaviruses are found in a variety of bird species. The term enterovirus-like viruses (ELVs) is used to identify this group of picornaviruses because they have not been completely characterized and classified. ELVs have been associated with several multicausal diseases, including enteritis and malabsorption syndrome. Diarrhea, stunted growth, decreased feed efficiency, and increased mortality rates in young chicks are the primary clinical signs. Diagnosis is based on histological examination, RT-PCR assay, and, in some cases, virus isolation. No treatments or vaccines are available.
Epidemiology and Transmission of Picornavirus Infections in Poultry
Enterovirus-like viruses have been found in a range of bird species, including commercial poultry and wild birds from several countries around the globe. ELVs have been linked with enteritis and stunting syndrome in young birds during the first few weeks of life; however, a number of reports have also found the viruses in clinically healthy birds. Therefore, the pathogenicity of ELVs requires further investigation. Pathogenesis of ELVs is believed to involve propagation and resultant destruction of gut epithelium, leading to malabsorption and enteritis. As reflected in their replication in intestinal mucosa, ELVs are predominantly transmitted by the fecal-oral route, although vertical transmission is also suspected.
Clinical Findings and Lesions of Picornavirus Infections in Poultry
Clinical signs of an enterovirus-like virus are frequently reported in the first few weeks of life and include diarrhea, stunted growth, and death. Affected birds may also show listlessness and fecal pasted vents.
Gross lesions are characteristic of enteric viral diseases and include intestinal dilation, thinning intestinal walls, and foamy intestinal or cecal contents. Microscopic lesions include shortening of villi, elongation of crypts, hyperplasia of enterocytes, and varying amounts of inflammatory cell infiltration into the lamina propria of the intestinal tract.
Diagnosis of Picornavirus Infections in Poultry
Transmission electron microscopy
Virus isolation
Histological examination
RT-PCR assay
Few laboratories offer routine diagnostic testing for enterovirus-like viruses due to the lack of characterization of this group of viruses and difficulty in primary isolation of the viruses. Transmission electron microscopy (TEM) has been used to detect ELVs in feces or intestinal samples from affected birds or isolated viruses. Results should be interpreted carefully because birds and eggs used for propagation (ie, even SPF birds) may already be infected with an ELV.
Enterovirus-like viruses often replicate poorly in cell culture but can be isolated or propagated in neonatal birds or embryonated eggs from the same bird species. Other challenges associated with isolation and propagation of ELVs include outgrowth of other intestinal viruses, especially reoviruses.
As advanced molecular techniques such as next-generation sequencing and metagenomics become increasingly available, characterization of ELVs may become a routine practice in the future.
Serological assays have been described for the detection of antibodies against some ELVs; however, these assays are not routinely used because the true pathogenicity and distribution of ELVs in commercial poultry have not been fully investigated.
Prevention and Treatment of Picornavirus Infections in Poultry
There is no treatment for enterovirus-like viruses, although supportive care (fluids and micronutrients) can decrease weight loss associated with infection. Currently, there is no commercial vaccine available for ELVs.
Zoonotic Risk of Picornavirus Infections in Poultry
No evidence of zoonotic transmission of picornavirus infections has been reported.
Key Points
Enterovirus-like viruses (ELVs) belong to the Picornaviridae family and are linked to enteric diseases in both commercial poultry and wild birds.
The role of ELVs in causing enteric diseases is unclear because the viruses are found in both healthy and affected birds.
No treatment or vaccines are available.
For More Information
Hayhow CS. Avian enterovirus-like virus infections. In: Swayne DE, ed. Boulianne M, Logue CM, McDougald LR, Nair V, Suarez DL, associate eds. Diseases of Poultry. 14th ed. Wiley; 2020: 421-425.
Pfleiderer L, Vaillancourt JP. Other viral enteric infections. In: Brugere-Picoux J, Vaillancourt JP, Shivaprasad HL, Venne D, Bouzouaia M, eds. Manual of Poultry Diseases. French Association for the Advancement of Science; 2015:194-199.
