Herpesviruses in selected groups of free-living birds

Ptice so gostitelji številnih herpesvirusov (HV). Okužba pri njih lahko ostane neopažena ali povzroči (letalno) bolezen. Za razliko od HV pri perutnini so podatki o okužbi, prisotnosti in vplivu HV na prostoživeče ptice skopi. Celotni seznam naravnih gostiteljev HV pri pticah ni poznan. Vzorce organov, orofaringealnih in/ali kloakalnih brisov 1212 živih in mrtvih prostoživečih ptic iz 15 redov smo pregledali na prisotnost odseka gena DNA polimeraze HV. HV smo dokazali v vzorcih organov osmih od 55 (14,5 %) pregledanih poginjenih sov, v brisih kloake štirih od 525 (0,7 %) pregledanih prostoživečih pevk, odlovljenih med jesensko selitvijo, v orofaringealnih in/ali kloakalnih brisih 34 od 447 (7,5 %) prostoživečih bolnih, poškodovanih ali oslabelih ptic, ki so potrebovale nujno veterinarsko pomoč in so bile sprejete na Kliniko za ptice, male sesalce in plazilce Veterinarske fakultete, in v orofaringealnih brisih 16 od 170 (9,4 %) živih prostoživečih sov, vzorčenih na območju Krima in Jelovice. HV smo odkrili tako pri poginjenih kot tudi pri živih, klinično zdravih prostoživečih pticah. V gnezdeči populaciji sov nismo ugotovili vpliva HV na produktivnost sov, saj se število jajc in mladičev med okuženimi in neokuženimi gnezdi ni razlikovalo. Filogenetska analiza nukleotidnih zaporedij odseka gena DNA polimeraze HV je pokazala, da se HV, dokazani pri prostoživečih pticah, uvrščajo v poddružino Alphaherpesvirinae in da v populaciji prostoživečih ptic v Sloveniji krožijo različni HV, ki se v večini primerov razlikujejo od že znanih HV, objavljenih v genski banki. Nekateri HV so specifični za gostiteljsko vrsto ptic, medtem ko smo v nekaterih primerih v različnih redovih ptic odkrili zelo podobna oziroma identična nukleotidna zaporedja, kar pomeni, da HV niso vedno omejeni na vrsto ptice. Do prenosa HV bi lahko prišlo s plenjenjem ptičjega plena ali celo s superplenilstvom. Ugotovili smo tudi, da mali glodavci kot plen ne predstavljajo vira okužbe s HV za ptice iz reda sov, sokolov in ujed. Z opravljenimi študijami smo močno razširili seznam dovzetnih gostiteljskih vrst prostoživečih ptic in ugotovili, da je za dokaz HV pri prostoživečih pticah z neznanim statusom okužbe treba odvzeti tako brise orofarinksa kot brise kloake.Birds are hosts of many herpesviruses (HVs), in which the infection can go unnoticed or cause (lethal) disease. In contrast to HV in poultry, data on infection with and the presence and impact of HV in wild birds are limited. In birds, the full list of natural hosts of HV is unknown. Samples of organs and oropharyngeal and/or cloacal swabs of 1,212 live and dead free-living birds from 15 orders were examined for the presence of a fragment of the HV DNA polymerase gene. HV was detected in organ samples in eight out of 55 (14.5%) dead owls, in cloacal swabs in four out of 525 (0.7%) free-living songbirds caught during the autumn migration, in oropharyngeal and/or cloacal swabs in 34 out of 447 (7.5%) free-living birds admitted as wildlife casualties to the Clinic for Birds, Small Mammals, and Reptiles at the Faculty of Veterinary Medicine, and in oropharyngeal swabs in 16 out of 170 (9.4%) live free-living owls sampled on Mount Krim and the Jelovica Plateau. HVs were detected in individuals found dead as well as in live individuals with no clinical signs of illness. Furthermore, no productivity deviances (i.e., in clutch and brood size) were recorded in a breeding population of clinical healthy owls. Phylogenetic analysis of nucleotide sequences of the partial DNA polymerase gene of HVs showed that HVs detected in free-living birds belong to the subfamily Alphaherpesvirinae and that different HVs have been circulating in the population of free-living birds in Slovenia, which in most cases are different from known HV nucleotide sequences published in GenBank. Some HVs are specific to the host bird species, whereas in some cases HVs very similar to identical nucleotide sequences were found in different bird orders, meaning that HVs are not always restricted to bird host species. HV transmission could occur through bird predation or even superpredation. It was also found that small rodents are not a source of HV infections in owls, falcons, and birds of prey. The results of the research greatly expand the list of HV-susceptible host species of free-living birds and show that free-living birds with unknown infection status should be tested with a combination of oropharyngeal and cloacal swabs, which would maximize the probability of HV detection

Detection of herpesviruses in passerine birds captured during autumn migration in Slovenia

ABSTRACT: Herpesviruses (HVs) were detected by PCR in the cloacal swabs of 0.76% (4/525) clinically healthy free-living passerine birds from 32 different species captured in mist nets in Slovenia during the 2014 and 2017 autumn migrations. Herpesviruses were detected in the Eurasian Blackcap (Sylvia atricapilla), the Common Blackbird (Turdus merula), and the Eurasian Blue Tit (Cyanistes caeruleus). Phylogenetic analysis of partial DNA polymerase gene nucleotide sequences of the HV strains showed a distant relationship with other alphaherpesviruses of birds. In the phylogenetic tree, the HVs detected were clustered together with HV detected in Sulphur-crested Cockatoo and Neotropic Cormorants, as well as with known HVs such as gallid HV1, Psittacid HV1 and HV2, and passerine HV1. Different sequences of HVs with relatively low identity were detected in our study, suggesting that different HVs were circulating in passerines sampled during the autumn migration in Slovenia

Herpesvirus infection in a breeding population of two coexisting strix owls

Abstract Birds are a frequent host of a large variety of herpesviruses, and infections in them may go unnoticed or may result in fatal disease. In wild breeding populations of owls, there is very limited information about the presence, impact, and potential transmission of herpesvirus. The herpesvirus partial DNA polymerase gene was detected using polymerase chain reaction in oropharyngeal swabs of 16 out of 170 owls examined that were captured in or near nest boxes. Herpesvirus was detected in Ural owls (Strix uralensis), in both adults and young, but not in tawny owls (Strix aluco). In yellow-necked mice (Apodemus flavicollis), as the main prey of tawny owls and Ural owls in the area, herpesvirus was detected in the organs of 2 out of 40 mice captured at the same locations as the owls. Phylogenetic analysis showed that the herpesvirus sequences detected in the Ural owls differed from the herpesvirus sequences detected in the yellow-necked mice. The results indicate that herpesvirus infection exists in the breeding wild Ural owl population. However, herpesvirus-infected owls did not show any clinical or productivity deviances and, based on a phylogenetic comparison of detected herpesvirus sequences and sequences obtained from Genbank database, it seems that mice and other rodents are not the source of owl infections. The most probable transmission pathway is intraspecific, especially from adults to their chicks, but the origin of herpesvirus in owls remains to be investigated

First report of Marek’s disease virus in commercial turkeys in Slovenia

Marek’s disease (MD), caused by Mardivirus gallidalpha 2 (GaAHV-2), also known as MD virus (MDV), is a lymphoproliferative disease that primarily affects chickens. Recently, MDV has been detected in lymphomatous tumors in turkeys in various countries. Between 2021 and 2023, three cases ranging from no to severe clinical disorders (depression, lameness, and increased mortality) occurred in commercial turkey flocks in Slovenia. In all cases, MDV was detected by PCR in DNA samples extracted from organs developing tumor infiltrations. Sequencing and phylogenetic analysis of the meq gene revealed that the GaAHV-2 detected has molecular features of a very virulent pathotype and genetic similarity with GaAHV-2 detected in chickens in Tunisia. This is the first report of MDV in commercial turkeys in Slovenia

Detection of laryngotracheitis virus in poultry flocks with respiratory disorders in Slovenia

Abstract Infectious laryngotracheitis (ILT) is an acute, highly contagious infectious disease of the upper respiratory tract in chickens and other poultry species that causes significant economic losses in countries worldwide. Between 2017 and 2019, seven outbreaks of mild to severe respiratory disorders with high suspicion of ILT occurred in commercial and backyard poultry flocks in Slovenia. In all submissions, infection with ILT virus (ILTV) was confirmed by PCR, which is the first report of ILT in Slovenia. Circulating ILT strains were characterized by the sequence and phylogenetic analysis of two fragments of the ICP4 gene. Four strains—three detected in non-vaccinated flocks and one in a flock vaccinated against ILT—were identical or very similar to the chicken embryo–origin live virus vaccines, and the other three were closely related to Russian, Chinese, Australian, and American field strains and to tissue culture origin vaccine strains. As in other diseases, coinfections with other respiratory pathogens in confirmed ILT cases may cause a more severe condition and prolong the course of the disease. In our study, coinfections with Mycoplasma synoviae (7/7 tested flocks), infectious bronchitis virus (5/5 tested flocks), Mycoplasma gallisepticum (4/7 tested flocks), Ornithobacterium rhinotracheale (3/4 tested flocks), and avian pox virus (1/2 tested flocks) were confirmed, indicating the importance of these pathogens in the occurrence of ILT infections

<i>Encephalitozoon cuniculi</i> Infection of Domestic Rabbits (<i>Oryctolagus cuniculus</i>) in Slovenia between 2017 and 2021

Encephalitozoon cuniculi is a microsporidial parasite that primarily infects domestic rabbits (Oryctolagus cuniculus). It is the causative agent of encephalitozoonosis, a disease with an internationally recognized seroprevalence among rabbits. This study determines the presence, clinical manifestation, and serological status of encephalitozoonosis in pet rabbits in Slovenia using various diagnostic procedures. From 2017 to 2021, 224 pet rabbit sera were collected and tested for encephalitozoonosis with the indirect immunofluorescence assay. Immunoglobulin M (IgM) and immunoglobulin G (IgG) antibodies against E. cuniculi were confirmed in 160 (65.6%) cases. Most seropositive rabbits suffered from neurological clinical signs or signs of gastrointestinal disorders such as recurrent hypomotilities, chronic weight loss, cachexia, or anorexia, and fewer showed clinical signs related to the urinary system or phacoclastic uveitis. A quarter of the positively tested rabbits presented without clinical signs. Hematological and biochemical blood analysis confirmed that seropositive animals had elevated globulin and deviated albumin levels in comparison to the normal reference values of non-infected animals. Furthermore, rabbits with neurological clinical signs showed statistically significant higher levels of globulins and total protein. Sixty-eight whole-body radiographs and thirty-two abdominal ultrasound reports were analyzed, looking for changes in the shape or size of the urinary bladder, presence of urinary sludge or uroliths, and any abnormalities related to the kidneys (shape, size, or nephrolites). The results suggest that neurological defects in the urinary bladder caused by E. cuniculi lead to a distended urinary bladder and consequently dysuria, incontinence, urine scalding, and sludgy urine

Evaluation of welfare in commercial turkey flocks of both sexes using the transect walk method

The study was conducted between March and September 2019 in six meat-type turkey flocks with similar management standard procedures using the transect walk method. The concept of the method is based on visual observation of the birds while slowly walking across the entire farm in predetermined transects. Each flock was evaluated at three different times during the fattening cycle: at 3 to 4, 12 to 13, and 19 to 20 weeks of age, and total number of males and females that were immobile or lame, had visible head, vent, or back wounds, were small, featherless, dirty, or sick, had pendulous crop, or showed aggression toward birds or humans were recorded. At each visit, NH$_3$ and CO$_2$ were measured within the facilities. In the first assessment, the most frequently observed welfare indicators were small size (0.87%) and immobility (0.08%). Males showed a significantly higher prevalence of small size (p < 0.01), sickness (p < 0.05), and dirtiness (p < 0.1) compared to females. In the second assessment, the most common findings in both sexes were dirtiness (1.65%) and poor feather condition (1.06%), followed by immobility (0.28%). Males were significantly dirtier (p < 0.001), had more immobile birds (p < 0.01) and birds with vent wounds (p < 0.1), but had fewer sick birds (p < 0.05). In the last assessment, an increase in immobile, lame, sick, and dead birds was recorded, indicating an increase in health problems. Higher CO$_2$ (3000 and 4433 ppm) and NH$_3$ (40 and 27.6 ppm) values were noted only at the first assessment in two facilities. Further analyses showed that slightly elevated NH$_3$ and CO$_2$ levels did not influence the occurrence of welfare indicators. This study is the first description of the welfare of commercial turkey flocks in Slovenia