Genetic differences among Moraxella bovis and Moraxella bovoculi isolates from infectious bovine keratoconjunctivitis (IBK) outbreaks in southern Brazil

First report of Moraxella oculi in Brazil in an infectious bovine keratoconjunctivitis outbreak

Infectious Bovine Keratoconjunctivitis (IBK) is a widespread ocular disease that affects dairy and beef cattle worldwide, caused by Gram-negative bacteria from the genus Moraxella. It is the most common eye disease in cattle, with symptoms including tearing, ocular pain, corneal opacity, photophobia, ulceration, and, in severe cases, permanent blindness. This study focused on characterizing Moraxella species in a 2022 IBK outbreak in Minas Gerais, Brazil. Ocular swabs from 18 symptomatic Holstein cattle were analyzed through colony isolation, physiological tests, and molecular techniques, including PCR-RFLP and sequencing. Results revealed one isolate of Moraxella bovoculi genotype 1 and five isolates of Moraxella oculi, marking the first report of the latter species in Brazil. This study represents the second report of Moraxella oculi isolation and the first in a country different from the initial report. Notably, Moraxella bovis was not isolated in this outbreak. All isolates exhibited susceptibility to the tested antibiotics. Comparative genomic analysis between the Brazilian Moraxella oculi isolate and the American strain (Tifton 1) revealed 99.5% similarity in the 16-23 S rRNA locus and 99.0% average nucleotide identity.

Development and evaluation of a multiplex polymerase chain reaction in real-time for differential diagnosis of Moraxella-induced keratoconjunctivitis in livestock

Background and Aim

Infectious bovine keratoconjunctivitis (IBK) is a prevalent ocular disease that affects livestock, leading to substantial economic losses due to reduced production and culling of infected animals. Moraxella spp. is common bacterial pathogens that can cause keratoconjunctivitis in livestock. Therefore, rapid and accurate diagnosis is crucial for effective treatment and disease control. This study aimed to develop a multiplex real-time polymerase chain reaction (mRT-PCR) assay for the detection and differentiation of Moraxella bovoculi, Moraxella ovis, and Moraxella bovis.

Materials and Methods

Three reference strains of Moraxella as positive controls and 36 lacrimal swab samples collected from cattle were used to evaluate the developed mRT-PCR assay DNA extraction that was performed using the RIBO-sorb DNA/RNA extraction kit. Primers and probes were designed using the SpeciesPrimer pipeline. The annealing temperature, primer and probe concentrations, and sensitivity and specificity of the assay were optimized.

Results

An mRT-PCR assay was developed to detect pathogens associated with IBK in cattle on the basis of optimized parameters. The specificity and sensitivity of this assay were confirmed using samples containing individual pathogens (O - M. ovis, B - M. bovis, and BO - M. bovoculi), combinations of two pathogens (O-B, B-BO, and O-BO), and when the DNA of all three pathogens was present in a single reaction (O-B-BO). The analytical sensitivity of mRT-PCR for detecting M. ovis and M. bovoculi DNA was 21 copies or 50 fg per reaction, whereas that for M. bovis was 210 copies or 500 fg per reaction. In addition, this assay has been tested on samples isolated from the affected eyes of cattle in the Akmola region of the Republic of Kazakhstan.

Conclusion

For the first time in the Republic of Kazakhstan, the proposed mRT-PCR assay for the simultaneous detection of three Moraxella spp. pathogens has been developed. This assay exhibits the required specificity and high sensitivity for m RT-PCR, facilitating the timely implementation of effective measures for disease control and the prevention of economic losses. These losses are linked to a reduction in livestock breeding value, a reduction in meat and milk production, a reduction in the reproductive performance of heifers, resulting in fewer offspring, as well as costs related to the treatment of affected animals.

Component Causes of Infectious Bovine Keratoconjunctivitis - The Role of Moraxella Species in the Epidemiology of Infectious Bovine Keratoconjunctivitis

Infectious bovine keratoconjunctivitis (IBK) involves multiple factors and opportunistic pathogens, including members of the genus Moraxella, specifically M bovis. The causal role of M bovis is clear, where the presence of virulence factors that facilitate colonization (pili) and host cytotoxicity (RTX toxins) are well characterized, and IBK has been reproduced in many models. Experimental infection with M bovoculi has failed to reproduce IBK-typical lesions in cattle thus far. However, recent work using genomics and mass spectrometry have found genomic diversity and recombination within these species, making species differentiation complex and challenging the ability to assign IBK causality to these organisms.

The epizootic situation of cattle moraxellosis in several economic entities of the Republic of Kazakhstan

BACKGROUND AND AIM

Infectious bovine keratoconjunctivitis (IBK; conjunctivitis) is a widespread eye disease in cattle. In 1960, the Gram-negative bacillus Moraxella bovis was discovered as one of IBK's etiological causal agents. This study aimed to clarify the epidemiological (epizootic) situation of cattle moraxellosis in the Republic of Kazakhstan. The study also maps the quantitative and qualitative indicators of the epidemiological (epizootic) process to develop more effective antiepizootic measures.

MATERIALS AND METHODS

We clinically examined both imported and local cattle species based on existing epidemiological (epizootological) units of economic entities in Kazakhstan. Then, we selected biomaterials for laboratory tests to screen for moraxellosis.

RESULTS

We clarified the epizootic situation for moraxellosis of cattle in Kazakhstan using data from the Meat Union of Kazakhstan, veterinary reports from the Veterinary Control and Surveillance Committee of the Ministry of Agriculture, Kazakhstan, and our results, obtained during visits to farms in the various regions of the republic.

CONCLUSION

Based on the data of the conducted studies, we developed epizootic visualization maps with quantitative indicators of the cattle moraxellosis epizootic-transfer processes within various regions of Kazakhstan for 2019. The data obtained from studies of the properties of the isolated cultures compared with the characteristics of reference strains gave grounds to classify them as belonging to the Moraxella genus.