Diagnosis of a mixed mycoplasma infection associated with a severe outbreak of bovine pinkeye in young calves

Randomized controlled field trial to assess the efficacy of an intranasal Moraxella bovis cytotoxin vaccine against naturally occurring infectious bovine keratoconjunctivitis

Background

Infectious bovine keratoconjunctivitis (IBK; pinkeye) is generally considered to be caused by corneal infections with Moraxella bovis. Previous studies demonstrated that M. bovis cytotoxin-specific mucosal immune responses in the bovine eye can be stimulated by intranasal vaccination with a recombinant M. bovis cytotoxin subunit adjuvanted with polyacrylic acid.

Methods

A randomized controlled field trial (two-arm parallel design with blinding) was conducted in beef steers in Northern California to determine if this vaccine could prevent naturally occurring IBK and/or reduce morbidity rates associated with this disease. Beef steers were vaccinated intranasally on days 0 and 21 with either a recombinant M. bovis cytotoxin subunit adjuvanted with polyacrylic acid (Vaccine group) or adjuvant alone (Control group). Eye examinations were performed on all steers every 7 days for 16 weeks to document the occurrence of IBK and to determine sizes of corneal ulcers. Serum and tear samples were collected on days 0, 42, and 112 from a subset of animals to measure changes in systemic and ocular immune responses to M. bovis cytotoxin.

Results

The cumulative proportion of steers that developed IBK after 16 weeks did not differ between groups. Variables related to disease severity were numerically lower in steers that received the experimental vaccine. IBK-affected Vaccine group steers had a significantly lower number of observation weeks with severe ulcers versus Control group steers. Cytotoxin-specific tear IgA was significantly higher in Vaccine group compared to Control group steers on day 112. Conclusion: Although the proportion of animals that developed corneal ulcers associated with IBK did not differ between groups, the lowered metrics of disease severity in vaccinated steers suggests that intranasal vaccination with recombinant M. bovis cytotoxin can reduce the severity of IBK in cattle.

Association of different microbes and pathogenic factors in cases of infectious bovine keratoconjunctivitis in cattle from Eastern Kazakhstan

Background and Aim

Infectious bovine keratoconjunctivitis (IBK) causes a significant economic loss to cattle industries in many countries, including Kazakhstan. Although Moraxella bovis is recognized as an etiologic agent of IBK, other bacterial and viral agents have been suspected to play a role in the pathogenesis of this disease. This study aimed to evaluate samples collected from the eyes of IBK-affected cattle in Eastern Kazakhstan at different stages of IBK for the presence of Mor. bovis, Moraxella bovoculi, Mycoplasma bovis, Mycoplasma bovoculi, and Bovine Herpes Virus Type 1 (BHV-1) and to characterize Mor. bovoculi pilA gene sequence diversity from Mor. bovoculi positive samples.

Materials and Methods

Individual ocular swabs (n = 168) were collected from cattle that had clinical signs of IBK during the summer of 2022 on farms in the Abay region of Kazakhstan. Eye lesion scores (1, 2, and 3) were assigned depending on the degree of ocular damage. Infectious bovine keratoconjunctivitis-associated organisms were detected using a multiplex real-time polymerase chain reaction assay. The Mor. bovoculi pilA gene was sequenced from Mor. bovoculi positive samples.

Results

Mycoplasma bovis and BHV-1 were not detected in any of the collected samples. Mycoplasma bovoculi was identified in the majority of samples overall, usually in mixed infection with Moraxella spp. Moraxella bovoculi was detected in 76.2% of animals and predominated in animals with eye lesion scores 2 and 3. Mycoplasma bovoculi was detected only in association with Mor. bovis and/or Mor. bovoculi in animals with eye lesion scores 2 and 3. Moraxella bovis was found in 57.7% of animals and was always identified in association with another organism. Sequencing of the pilA gene in 96 samples from Mor. bovoculi positive samples identified five PilA groups. The majority belonged to PilA group A. However, three new PilA groups were identified and designated PilA groups N, O, and P.

Conclusion

The results indicate a high prevalence of Myc. bovoculi and Mor. bovoculi in eyes of cattle with IBK on livestock farms in Eastern Kazakhstan. Additional novel Mor. bovoculi PilA groups were identified.

Investigation of the pathogens contributing to naturally occurring outbreaks of infectious bovine keratoconjunctivitis (pinkeye) using Next Generation Sequencing

Infectious bovine keratoconjunctivitis (IBK), commonly known as pinkeye, has a marked negative impact on the economy of the cattle industry. Moraxella species, including Mor. bovis and Mor. bovoculi, which have been associated with this disease, colonize clinically healthy eyes as well, suggesting that there are intrinsic changes that may occur to the ocular microbiota or the involvement of additional unrecognized organisms that contribute to IBK. To evaluate this, 104 ocular swabs collected from eyes with IBK or clinically healthy eyes from 16 different cattle herds were subjected to 16 S rRNA gene PCR and next generation sequencing (NGS) analysis. Organisms detected were similar across the herds and there was no difference in the total number of bacterial groups detected among IBK cases and controls. However, the percentages of the different organisms detected varied between the two groups, including Moraxella spp., with more Moraxella spp. in eyes with IBK than controls. Further, using culture and whole genome NGS, a new species of Moraxella (suggested name Mor. oculobovii) was detected from the eyes of cattle from two farms. This strain is non-hemolytic on blood agar, is missing the RTX operon, and is likely a non-pathogenic strain of the bovine ocular microbiome. Alteration of the ocular microbiota composition may have a predisposing role, enhancing bacterial infection and the occurrence of clinical IBK. Future studies are required to evaluate if these changes are permanent or if there is a shift in the microbiome following recovery from the infection and how antibiotics might affect the microbiome.

A Review of Global Prevalence and Economic Impacts of Infectious Bovine Keratoconjunctivitis

A summary of available literature on the prevalence and estimated economic impacts of infectious bovine keratoconjunctivitis (IBK) from around the world is made. Country-level prevalence of IBK has been reported only for the United States, Australia, and New Zealand. We provide an estimate of IBK prevalence rate by geographic climate and region accounting for cattle sub-species and age. Estimated prevalence worldwide is 2.78%. Historical economic impact assessments are available only for the United States, Australia, and United Kingdom. Rarely do assessments capture the full economic cost of the disease. Better data on prevalence and how treatment and prevention decisions modify disease impacts is required to estimate the global economic impact.

Component Causes of Infectious Bovine Keratoconjunctivitis-Non-Moraxella Organisms in the Epidemiology of Infectious Bovine Keratoconjunctivitis

Infectious bovine keratoconjunctivitis (IBK) is a multifactorial disease complex caused by opportunistic pathogens, classically those members of the genus Moraxella. However, IBK in some situations is associated with other potentially pathogenic agents, which include Mycoplasma bovoculi, Mycoplasma bovis, Ureaplasma diversum, bovine herpesviruses, and Chlamydia sp. Ocular infections that may resemble IBK are also caused by Listeria monocytogenes. These agents and their association with IBK are reviewed in this article.

Swine conjunctivitis outbreaks associated with Mycoplasma hyorhinis

Conjunctivitis is an uncommon finding in commercial swine herds, and the etiology of the disease is rarely studied. We investigated cases of conjunctivitis in 3 wean-to-finish swine farms. Eye swabs and tissues were obtained from clinically affected pigs (8-22 wk of age), from unaffected pigs in contact with affected pen-mates, and from age-matched pigs from an unaffected herd. Real-time PCR (rtPCR) testing for Mycoplasma hyorhinis demonstrated consistent detection and high bacterial load in samples from affected herds (clinically affected animals and non-clinical pen-mates). Ct values in affected pigs were 18.9-25.3; values were 36.4-38.6 in unaffected pigs from unaffected herds. Additionally, M. hyorhinis was identified within inflamed palpebral conjunctivae by in situ hybridization. The association of rtPCR and in situ detection of M. hyorhinis, along with the lack of detection of other potential pathogens and noninfectious causes, suggests the involvement of M. hyorhinis in the etiology and pathogenesis of the reported swine conjunctivitis.

A multiplex real-time PCR assay for the detection and differentiation of five bovine pinkeye pathogens

Infectious bovine keratoconjunctivitis (IBK), also known as pinkeye, is one of the most common eye diseases in cattle. Several pathogens have been associated with IBK cases, however, Moraxella bovis, Moraxella bovoculi, Mycoplasma bovis, Mycoplasma bovoculi and bovine herpesvirus type 1 (BHV-1) are most frequently observed. A multiplex real-time PCR assay using two reactions was developed for the detection and differentiation of these five pathogens. Detection sensitivities of the multiplex assays were compared to singleplex reactions testing for the same targets. Correlation coefficients (R²) of >0.99, and PCR efficiencies between 92 and 106% were demonstrated in all singleplex and multiplex real-time PCR reactions. The limits of detection (LOD) of multiplex assays for Moraxella bovis, Moraxella bovoculi, Mycoplasma bovis, Mycoplasma bovoculi and BHV-1 were 19, 23, 25, 24 and 26 copies per reaction, respectively. No cross amplification was observed for specificity testing of 179 IBK positive clinical samples and 55 non-target clinical samples. Percentage of clinical samples positive for Mycoplasma bovoculi, Moraxella bovoculi, Moraxella bovis, BHV-1 and Mycoplasma bovis were 88.8% (159/179), 75.9% (136/179), 60.3% (108/179), 11.7% (21/179) and 10.0% (18/179), respectively. Moraxella bovis, Moraxella bovoculi and Mycoplasma bovoculi were more prevalent than Mycoplasma bovis and BHV-1 in IBK samples collected from animals in this study population. Our data indicates that the multiplex real-time PCR panel assay is highly sensitive and highly specific for the detection and differentiation of the five major pathogens associated with bovine pinkeye.

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A multiplex real-time PCR is developed for the detection of five major IBK pathogens.

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Correlation coefficients of all standard curves were >0.99.

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PCR amplification efficiencies for the five pathogens were between 92% and 106%.

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Limits of detection were between 19 and 26 copies per reaction for the five pathogens.

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Moraxella bovoculi, Mycoplasma bovoculi, and Moraxella bovis were more prevalent IBK pathogens.

Whole genome sequencing of Moraxella bovoculi reveals high genetic diversity and evidence for interspecies recombination at multiple loci

Moraxella bovoculi is frequently cultured from the ocular secretions and conjunctiva of cattle with Infectious Bovine Keratoconjunctivitis (IBK). Previous work has shown that single nucleotide polymorphism (SNP) diversity in this species is quite high with 81,284 SNPs identified in eight genomes representing two distinct genotypes isolated from IBK affected eyes (genotype 1) and the nasopharynx of cattle without clinical IBK signs (genotype 2), respectively. The goals of this study were to identify SNPs from a collection of geographically diverse and epidemiologically unlinked M. bovoculi strains from the eyes of IBK positive cattle (n = 183) and another from the eyes of cattle (most from a single population at a single time-point) without signs of IBK (n = 63) and to characterize the genetic diversity. Strains of both genotypes were identified from the eyes of cattle without IBK signs. Only genotype 1 strains were identified from IBK affected eyes, however, these strains were isolated before the discovery of genotype 2, and the protocol for their isolation would have preferentially selected genotype 1 M. bovoculi. The core genome comprised ~74% of the whole and contained >127,000 filtered SNPs. More than 80% of these characterize diversity within genotype 1 while 23,611 SNPs (~18%) delimit the two major genotypes. Genotype 2 strains lacked a repeats-in-toxin (RTX) putative pathogenesis factor and any of ten putative antibiotic resistance genes carried within a genomic island. Within genotype 1, prevalence of these elements was 0.85 and 0.12 respectively in strains from eyes that were IBK positive. Recombination appears to be an important source of genetic diversity for genotype 1 and undermines the utility of ribosomal-locus-based species identification. The extremely high genetic diversity in genotype 1 presents a challenge to the development of an efficacious vaccine directed against them, however, several low-diversity pilin-like genes were identified. Finally, the genotype-defining SNPs described in this study are a resource that can facilitate the development of more accurate M. bovoculi diagnostic tests.

DNA microarray assay and real-time PCR as useful tools for studying the respiratory tract Mycoplasma populations in young dairy calves

PURPOSE

With more than 120 species, the genus Mycoplasma is one of the largest taxa in the class Mollicutes, a group of micro-organisms that are characterized by apparent simplicity and to which important animal pathogens belong. Mycoplasmabovis is the most frequently identified pathogenic Mycoplasma in cattle; however, the prevalence of other Mycoplasma species living in calves' airways is poorly understood. The aim of this work was to characterize the respiratory tract mycoplasma populations in calves on one of the largest dairy farms in Italy using a real-time PCR assay and a DNA microarray assay.

METHODOLOGY

A total of 49 nasal swabs and 49 trans-tracheal aspirations from non-vaccinated veal calves were analysed. Genomic DNA was extracted from the samples and then tested using a real-time PCR targeting the oppD gene of M. bovis and a DNA microarray that was able to identify more than 70 Mycoplasma species.

RESULTS

Forty-two out of 49 calves tested positive for Mycoplasma spp. (85.7 %). None of the samples tested positive for M. bovis. A majority (73.5 %) of the 98 samples tested positive for M. dispar, while 8 samples tested positive for M. bovirhinis (8.2 %).

CONCLUSION

Our results expand our knowledge regarding the diversity of Mycoplasma populations in the respiratory airways of very young veal calves and add data regarding M. bovis prevalence in the Italian cattle population. However, the importance of these species in the respiratory diseases of calves still remains to be determined.

Microbial community sequencing analysis of the calf eye microbiota and relationship to infectious bovine keratoconjunctivitis

Infectious bovine keratoconjunctivitis (IBK) is an important production limiting disease in cattle. Moraxella bovis has historically been considered the primary causal agent; however, vaccines have not been consistently shown as effective in controlling disease incidence. The purpose of this study was to examine the bacterial community of calf eyes prior to disease onset using high-throughput sequencing of 16S ribosomal RNA and determine if it was associated with IBK occurrence. The study was designed as a case-control nested within a randomized controlled trial (RCT). Eye swabs were collected from all spring-born calves without clinical signs of IBK (t₀ swabs) on a research farm with a previous history of IBK disease outbreaks. At follow-up or weaning, calves were diagnosed as IBK positive or negative. The lag time between enrollment swabs (t₀) and IBK diagnosis ranged from approximately one to three months. Cases were randomly selected from IBK positive calves and controls were selected from IBK negative calves (i.e. calves that did not exhibit clinical signs of IBK throughout the course of the RCT). Analysis of the fold-change differences between cases and controls did not reveal large-scale distinctions in bacterial composition. However, principal component analysis suggested bacterial composition differences between calf management groups, which were based on dam parity. Moraxella was found to be among the top ten most abundant genera in our population; however, the difference in abundance was not significant between the cases and controls. No large-scale differences in the bacterial communities of calves that did or did not develop IBK were observed in our population. Nevertheless, it remains unclear whether the "natural" bacterial population of the calf might ultimately impact disease status. Further study is warranted to examine bacterial taxa that were observed to be significantly more abundant in the cases or controls as potential vaccines/therapeutic targets.

Molecular and Antigenic Characterization of a Mycoplasma Bovis Strain Causing an Outbreak of Infectious Keratoconjunctivitis

An unusually high incidence of infectious keratoconjunctivitis followed by pneumonia and arthritis was observed in beef calves of a managed herd. No Moraxella spp. or bacteria other than Mycoplasma spp. were obtained from conjunctival and nasal swabs. A strategy was designed for characterization of bovine mycoplasmas at species and strain level on the basis of a combination of molecular tools and the immunoblotting method. The strategy made it possible to rapidly assign the bacterium responsible for this outbreak to one of the phylogenetic clusters of bovine mycoplasmas delineated in this study and then to identify it as Mycoplasma bovis. The strain, designated Sar 1, showed a 100% 16S rDNA sequence identity with two European strains (120/81 and MC3386) isolated in Germany and Ireland, respectively, and hosts a vsp gene analog to the vspA, vsp422-4, and vsp422-8 genes of the M. bovis reference strain PG45T and of the field strain 422. The use of a cross-reactive rabbit serum developed against the Mycoplasma agalactiae immunodominant antigen P48 confirmed the molecular findings. The immunological response of calves against M. bovis was also investigated. This is the first report on the occurrence of M. bovis on the Island of Sardinia (Italy).

Infectious bovine keratoconjunctivitis (pinkeye)

As is the case for controlling other infectious livestock diseases, the most successful efforts to control infectious bovine keratoconjunctivitis (IBK) will include consideration of the host, the environment, herd management, and ongoing surveillance even after the immediate crisis has passed. Research over many years has led to the discovery of a variety of antibiotic treatments and antibiotic regimens that can be effective against IBK. The discoveries of Mor bovoculi and reports of IBK associated with Mycoplasma spp without concurrent Mor bovis or Mor bovoculi have raised new questions into the roles that other organisms may play in IBK pathogenesis.

Point prevalence of infection with Mycoplasma bovoculi and Moraxella spp. in cattle at different stages of infectious bovine keratoconjunctivitis

Infectious bovine keratoconjunctivitis (IBK) has significant economic consequences and a detrimental impact on animal welfare. Although Moraxella (Mor.) bovis is the primary causative agent, the role of other bacteria, such as Mor. ovis, Mor. bovoculi and Mycoplasma (Myc.) bovoculi, is not well understood. To assess the prevalence of infection with these organisms, and to correlate this with outbreaks of IBK, conjunctival samples from four herds of cattle in Germany of differing IBK status were examined. Herds were selected to represent a hypothetical course of IBK ranging from the pre-outbreak stage (herd 1), to the acute disease stage (herd 2), to a stage where treatment had ceased (herd 3). Unaffected animals were also included (herd 4). To facilitate effective, sensitive sample analysis, a new real-time PCR for Myc. bovoculi was developed and used in concert with established real-time PCR protocols for Myc. bovis and Moraxella spp. Herds 1 and 2 showed similarly high rates of detection for Myc. bovoculi (92.5% and 84.0%, respectively), whereas herds 3 and 4 had a lower prevalence (35.5% and 26.2%, respectively). Mor. bovis and Mor. ovis were more prevalent in herd 1 (32.5% and 87.5%, respectively) and herd 2 (38% and 58%, respectively) than herd 3 (10.4% and 1.3%, respectively) and herd 4 (9.8% and 31.1%, respectively). Mor. bovoculi was the only pathogen that correlated with clinical signs of IBK; at 20% prevalence, it was almost exclusively detected in herd 2. The results indicate that herds with high Myc. bovoculi prevalence are more predisposed to outbreaks of IBK, possibly due to a synergistic interaction with Moraxella spp.

A novel rapid DNA microarray assay enables identification of 37 Mycoplasma species and highlights multiple Mycoplasma infections

Mycoplasmas comprise a conglomerate of pathogens and commensals occurring in humans and animals. The genus Mycoplasma alone contains more than 120 species at present, and new members are continuously being discovered. Therefore, it seems promising to use a single highly parallel detection assay rather than develop separate tests for each individual species. In this study, we have designed a DNA microarray carrying 70 oligonucleotide probes derived from the 23S rRNA gene and 86 probes from the tuf gene target regions. Following a PCR amplification and biotinylation step, hybridization on the array was shown to specifically identify 31 Mycoplasma spp., as well as 3 Acholeplasma spp. and 3 Ureaplasma spp. Members of the Mycoplasma mycoides cluster can be recognized at subgroup level. This procedure enables parallel detection of Mollicutes spp. occurring in humans, animals or cell culture, from mono- and multiple infections, in a single run. The main advantages of the microarray assay include ease of operation, rapidity, high information content, and affordability. The new test's analytical sensitivity is equivalent to that of real-time PCR and allows examination of field samples without the need for culture. When 60 field samples from ruminants and birds previously analyzed by denaturing-gradient gel electrophoresis (DGGE) were tested by the microarray assay both tests identified the same agent in 98.3% of the cases. Notably, microarray testing revealed an unexpectedly high proportion (35%) of multiple mycoplasma infections, i.e., substantially more than DGGE (15%). Two of the samples were found to contain four different Mycoplasma spp. This phenomenon deserves more attention, particularly its implications for epidemiology and treatment.

Antimicrobial susceptibilities of four species of Mycoplasma isolated in 2008 and 2009 from cattle in Japan

We examined the susceptibility in vitro of 99 isolates of Mycoplasma (M. bovirhinis, M. bovis, M. alkalescens and M. bovoculi) and one of Acholeplasma laidlawii collected in 2008 and 2009 from Japanese homebred cattle and cows imported from Australia to 13 antimicrobial agents. Mycoplasma species isolated from homebred cattle were susceptible to spectinomycin and fluoroquinolones but resistant to macrolides, tetracyclines, thiamphenicol and flumequine. Kanamycin, lincomycin and chloramphenicol maintained intermediate effectiveness against these species. The isolates from the imported cows maintained sufficient susceptibility to all antimicrobials examined except for erythromycin and thiamphenicol. These results showed that four species of Mycoplasma isolated from Japanese homebred cattle had obviously higher drug resistance compared with previous reports, even within this decade.

Mycoplasma bovis Infections in young calves

Mycoplasma bovis has emerged as an important pathogen of young intensively reared calves in North America. A variety of clinical diseases are associated with M bovis infections of calves, including respiratory disease, otitis media, arthritis, and some less common presentations. Clinical disease associated with M bovis often is chronic, debilitating, and poorly responsive to antimicrobial therapy. Current control measures are centered on reducing exposure to M bovis through contaminated milk or other sources, and nonspecific control measures to maximize respiratory defenses of the calf. This article focuses on the clinical and epidemiologic aspects of M bovis infections in young calves.

An Outbreak of Chronic Pneumonia and Polyarthritis Syndrome Caused by Mycoplasma Bovis in Feedlot Bison (Bison Bison)

Mycoplasma bovis was identified by a specific lesion, conventional bacterial culture, immunohistochemistry, and polymerase chain reaction in 2 feedlot bison found dead with severe, chronic, caseonecrotic pneumonia; polyarthritis; and laryngitis. On microscopic examination, pulmonary lesions were characterized by prominent, well-defined areas of caseous necrosis and bronchiectasis. Immunohistochemical analysis of lung exhibited staining in bronchiolar epithelium and in random areas of caseous necrosis. On gross examination, the laryngeal lesion observed in 1 animal was typical of changes seen in cases of calf diphtheria. Nasal swabs taken from 6 clinically ill bison from the same feedlot revealed 1 animal shedding M. bovis by the nasal route. No other pathogens were recovered from the pulmonary or laryngeal lesions; however, Mannheimia haemolytica was cultured from the nasal swabs of 2 clinically ill bison, although not from the animal found to be shedding M. bovis. Several other affected bison had swollen joints and exhibited lameness and a reluctance to move. Changes observed in dead and clinically ill bison from this feedlot are similar to what has been described in the literature as chronic pneumonia and polyarthritis syndrome in feedlot cattle caused by M. bovis. Based on the severity of the lesions, and the number of dead and affected animals, bison in a feedlot setting appear to exhibit sensitivity to infection with M. bovis.

Mycoplasma bovis pneumonia in cattle

Mycoplasma bovis is an important and emerging cause of respiratory disease and arthritis in feedlot cattle and young dairy and veal calves, and has a variety of other disease manifestations in cattle. M. bovis is certainly capable of causing acute respiratory disease in cattle, yet the attributable fraction has been difficult to estimate. In contrast, M. bovis is more accepted as a cause of chronic bronchopneumonia with caseous and perhaps coagulative necrosis, characterized by persistent infection that seems poorly responsive to many antibiotics. An understanding of the disease has been recently advanced by comparisons of natural and experimentally induced disease, development of molecular diagnostic tools, and understanding some aspects of virulence, yet uncertainties regarding protective immunity, the importance of genotypic diversity, mechanisms of virulence, and the role of co-pathogens have restricted our understanding of pathogenesis and our ability to effectively control the disease. This review critically considers the relationship between M. bovis infection and the various manifestations of the bovine respiratory disease complex, and addresses the pathogenesis, clinical and pathologic sequelae, laboratory diagnosis and control of disease resulting from M. bovis infection in the bovine respiratory tract.

Nonrespiratory diseases of stocker cattle

Bovine respiratory disease is the most common health issue affecting stocker cattle. There are several nonrespiratory diseases that affect stockers. The more common diseases include rumen tympany, infectious bovine keratoconjunctivitis, coccidiosis, photosensitization, and foot rot. Accurate diagnosis, early treatment, and incorporating appropriate preventive measures can assist cattle production.

The detection of an unidentified type of adenovirus in the stools of calves with weak calf syndrome by use of a commercial kit designed for the detection of human adenoviruses

An outbreak of polyarthritis in newborn calves in a large collective dairy herd was characterized by intra‐articular blood‐tinged synoviae, blood tainted faeces and massive subcorneal haemorrhages. Faecal samples from eight clinical newborn cases, 10 from unrelated dairy farms and 10 faecal samples from healthy calves were examined by the Rida^® Quick rotavirus/adenovirus‐combi test . A specific adenovirus antigen precipitin‐line was seen in the reaction in all the faecal samples from the diseased calves (n = 8), while all the others (n = 20) were negative. In addition, the same positive reaction was noted when one aqueous humor and two synovial samples were tested with this kit. Several other enteropathogens were found sporadically, but no conclusive significance could be attributed to their presence. Bovine viral diarrhoea and infectious bovine rhinothracheitis viruses as well as Chlamydia spp. and Mycoplasma spp. were not involved in this episode.