Herpesvirus infection of pigeons. I. Pathology and virus isolation

A retrospective study of pigeon herpesviral infection in domestic pigeons in California (1991-2014) and literature review

We characterized naturally occurring pigeon herpesvirus (PiHV; Columbid alphaherpesvirus 1) infection in domestic pigeons in California. We retrieved and analyzed 62 pathology reports produced between 1991 and 2014 at the California Animal Health and Food Safety Laboratory System. In 56 of the cases, the diagnosis of PiHV infection was established based on histopathology, either alone (44 cases) or combined with virus isolation (VI; 8), transmission electron microscopy (TEM; 3), or PCR (1); in the remaining 6 cases, the diagnosis was established based on VI (5 cases) or TEM (1) alone. PiHV infection affected 1 system in 34, 2 in 16, and ≥3 systems in 6 cases; data were not available for the remaining 6 cases. Most commonly affected was the digestive system (55 cases), followed by the respiratory tract (5) and lymphoid system (2). The liver (39 cases), crop (17), and esophagus (14) were the organs affected most commonly. Many affected cells often bore single eosinophilic intranuclear inclusion bodies. PiHV infection was a secondary diagnosis or incidental finding in 35 cases. Most (55) cases had 1 (21), or up to 4 (34), other concurrent infections; the most common concurrent infections were pigeon circoviral infection (26), trichomonosis (24), aspergillosis (11), and colibacillosis (10).

Co-occurrence of Mycoplasma Species and Pigeon Herpesvirus-1 Infection in Racing Pigeons ( Columba livia)

Oropharyngeal swab samples were collected from 438 live racing pigeons ( Columba livia), with and without signs of respiratory disease, that were housed in 220 lofts in 3 provinces in the western part of the Netherlands. Polymerase chain reaction (PCR) was used to identify Mycoplasma species and pigeon herpesvirus-1 (PHV-1) from the samples. In 8.6% of the pigeon lofts tested, signs of respiratory disease were present in pigeons at sampling, and in 30.9% of the sampled pigeon lofts, respiratory signs were observed in pigeons during the 6-month period immediately before sampling. A total of 39.8% of tested pigeons (54.5% of tested lofts) were positive for Mycoplasma species, and 30.6% of tested pigeons (48.6% of tested lofts) were positive for PHV-1. In 15.8% of the tested pigeons (26.8% of tested pigeon lofts), coinfection by Mycoplasma species and PHV-1 was identified. The number of pigeon lofts having pigeons coinfected by Mycoplasma species and PHV-1 was higher than that where only one of the infections was identified. Neither the presence of Mycoplasma species, PHV-1, nor the co-occurrence of both infections was significantly associated with signs of respiratory disease.

Studies on reactivation and transmission of pigeon herpes virus (PHV) for raising PHV-free pigeons (Columba livia dom.)

For raising pigeons free of herpes virus infection, 12 parental pigeons were monitored for shedding of pigeon herpes virus (PHV) during 18 weeks of reproduction. In most of the birds only a sporadic virus excretion, which was never associated with clinical signs could be observed. However, three out of seven squabs raised by their parents became infected during the first 3 weeks of life and all seven became PHV seropositive within 4 months. Therefore, we raised seven squabs hatched in an incubator by hand using heat-inactivated crop milk. By this method we were able to obtain pigeons free of PHV infection, i.e. no virus could be isolated during the first 5 weeks of life and they remained seronegative during an observation period of 8 months. These animals have been assigned to breed a live-stock of PHV -free pigeons, necessary for studies on the pathogenesis of PHV and other pathogens.

Isolation of viruses from clinical outbreaks of inclusion body hepatitis

Sixteen outbreaks of inclusion body hepatitis (IBH) in fowls were investigated. Most cases occurred in broilers, and birds 4-9 weeks old were affected. Mortality occurred over a period of 3-5 days, and reached 5% in some cases. The main pathological finding was a diffuse and generalised hepatitis, with eosinophilic intranuclear inclusions in the hepatocytes. From these outbreaks 46 adenoviruses and 6 reoviruses were isolated. The adenoviruses were classified into 5 serological types. Two outbreaks of IBH in pigeons were also examined. Herpesviruses and adenoviruses were isolated from both cases. It was possible to assign one adenovirus isolate to a known fowl adenovirus serotype.

Detection of new DNA polymerase genes of known and potentially novel herpesviruses by PCR with degenerate and deoxyinosine-substituted primers

A consensus primer PCR approach was used to (i) investigate the presence of herpesviruses in wild and zoo equids (zebra, wild ass, tapir) and to (ii) study the genetic relationship of the herpesvirus of pigeons (columbid herpesvirus 1) to other herpesvirus species. The PCR assay, based on degenerate primers targeting highly conserved regions of the DNA polymerase gene of herpesviruses, was modified by using a mixture of degenerate and deoxyinosine-substituted primers. The applicability of the modification was validated by amplification of published DNA polymerase genes of 16 herpesvirus species and of the previously uncharacterized DNA polymerase genes of equine herpesvirus 3 (EHV-3) and equine herpesvirus 5 (EHV-5). The modified assay was then used for partial amplification of the polymerase of columbid herpesvirus 1 which is presently classified as a beta-herpesvirus based on biological criteria. Sequence analysis of amplicons obtained from four different viral strains revealed a close relationship of columbid herpesvirus 1 to members of the subfamily Alphaherpesvirinae, especially to Marek's disease herpesvirus. This was confirmed by characterization of additional 1.6kb of the columbid herpesvirus 1 polymerase. Consensus PCR analysis of blood samples from zebras, a wild ass and a tapir revealed amplicons showing high percentages ( > 50%) of sequence identity to DNA polymerases of gamma-herpesviruses. In particular, the zebra and the wild ass sequence were closely related to each other and to the polymerases of the equine gamma-herpesviruses EHV-2 and EHV-5 with sequence identities of > 80%. This is a first indication that novel gamma-herpesviruses are present in wild and zoo equids.

Observation of Pigeon herpesvirus 1 re-excretion during the reproduction period in conventionally reared homing pigeons

Pigeon herpesvirus 1 (PHV1) re-excretion by latently infected mature homing pigeons was followed during the reproduction period under natural conditions. All latently infected pigeons re-excreted PHV1 during the reproduction period and most of them during squab-gorging.

An outbreak of disease in pigeons associated with a herpesvirus

An outbreak of disease in young pigeons associated with a herpesvirus is reported. The clinical history, macroscopic and microscopic appearance of lesions and virus isolation are described. Most affected birds showed lesions in the upper alimentary tract epithelium as well as in skin, nasal mucosa and salivary glands. Lesions in liver, spleen and pancreas were uncommon. A herpesvirus capable of producing CPE on tissue culture and lesions on chorioallantoic membrane of developing chicken embryos was isolated and described. Inoculation of experimental pigeons with the virus failed to reproduce the disease.