First Survey on the Presence and Distribution of Oxytetracycline-Resistance Genes in Anaplasma Species

A review of bovine anaplasmosis (Anaplasma marginale) with emphasis on epidemiology and diagnostic testing

Bovine anaplasmosis, caused by the rickettsia Anaplasma marginale, is an economically important tick-borne disease of cattle that is found worldwide. Its clinical effects of severe anemia, decreased growth, weight loss, and death negatively impact cattle welfare and create a significant economic burden for cattle producers. Despite availability of highly sensitive and specific assays for anti-A. marginale antibodies (competitive ELISA) and A. marginale genetic material (real-time PCR), the interpretation of test results for the diagnosis of clinical anaplasmosis in cattle remains challenging. Treatment and control usually consist of administration of oral and/or injectable tetracyclines; however, this approach is unlikely to be sustainable in the face of increasing scrutiny of antimicrobial usage in livestock. Statistically robust prospective studies are needed to characterize the prevalence, distribution, and transmission of bovine anaplasmosis under field conditions, as the epidemiology of this disease remains incompletely understood. Apart from minimizing exposure of naïve cattle to carriers (e.g., testing new introductions and interpreting in the context of herd-level seropositivity, changing needles between cattle), veterinarians and producers have few tools for prevention of bovine anaplasmosis based on data-driven risk assessment. A vaccine that is consistently safe and effective has proved elusive, but ongoing research into A. marginale vaccine candidates offers hope for a more effective means of protecting cattle from this costly disease.

Risk Factors Associated with Hemoparasites in Dual-Purpose Cattle of Colombia

Hemoparasitic diseases represent a significant problem with a considerable impact on tropical and subtropical areas of the world. These conditions cause economic losses associated with multi-organic failure and even the death of animals. In these areas, the hemoparasites are transmitted in an enzootic cycle when infectious cattle, such as persistently infected animals, including cows, contribute to the success of transmission. However, the factors associated with transmission have always been considered environmental issues, disregarding herd management and practices. In this sense, we conducted a cross-sectional study sampling 360 female cattle older than one year to identify infectious cattle using the PCR technique. We employed a dichotomic questionnaire for association analyses in 150 herds of the southern Andean region of Colombia. Overall prevalence with infectious cattle was 52.5% for Babesia spp., Anaplasma spp., and Trypanosoma spp., and the significant risk factors (p < 0.05) included geographic area, animal weight, purchase of cattle for fattening, disinfection of clothing after contact with neighboring animals, self-medication, separation of animals in pens, supply of mineralized salt, presence of livestock from other owners on the farm, prevention of joint trauma, documented milking routine, and sending blood samples for analysis. These practices permitted the maintenance of persistently infected animals and their movement to shed the agents to other animals in the presence of vectors. This suggests the importance of implementing comprehensive control and training measures to reduce the infectious cattle and, therefore, the profitability of dual-purpose livestock farms in the Andean region of southwestern Colombia.

Improvements in Blood Profiles of Canines Naturally Infected with Triple Blood Pathogens (Babesia vogeli, Ehrlichia canis, and Anaplasma platys) Subsequent to Doxycycline Monotherapy

Multiple blood pathogen infections are increasingly found in many areas, particularly in tropical regions. This study aimed to investigate the effectiveness and safety of using doxycycline monotherapy to treat triple blood pathogen infection in sheltered dogs. A total of 375 sheltered dogs were screened for blood pathogen using polymerase chain reaction technique (PCR). There were 34 dogs with triple infection (Babesia vogeli, Ehrlichia canis, and Anaplasma platys), and most dogs displayed anemia and thrombocytopenia. These dogs were treated with doxycycline (10 mg/kg/day) orally for four weeks, and their blood profiles were monitored. Almost all pathogens were undetectable by PCR by day 14 and pathogens were all cleared by day 28. Most blood profiles significantly improved after 14 days. The improvement continued after 28 days. The red blood cell and platelet count (PLT) were increased in similar trends between mild-to-moderate and severe thrombocytopenia groups. The average PLT in the mild-to-moderate thrombocytopenia group raised to normal level by day 14, whereas in the severe group, it was gradually increased to normal level by day 70. We propose using doxycycline monotherapy for 28 days to eliminate all pathogens, and facilitate recovery and welfare in dogs suffering with triple blood pathogen infections.

Molecular identification, risk factor assessment, and phylogenetic analysis of tick-borne pathogens in symptomatic and asymptomatic cattle from South-Eastern Iran

Tick-borne pathogens (TBPs) represent a substantial threat to cattle globally, exerting adverse impacts on production, health, and economic viability. This study delves into the prevalence and implications of TTBPs in cattle sourced from resource-limited smallholder livestock farms situated in southeastern Iran, proximate to Afghanistan and Pakistan. Blood and tick specimens were systematically collected from a cohort of 230 cattle, comprising 150 asymptomatic and 80 symptomatic individuals. Genomic DNA isolated from blood samples underwent rigorous examination for the presence of key TBPs, including Anaplasma marginale, A. phagocytophilum, A. bovis, A. centrale, Babesia bigemina, and Theileria annulata, utilizing multiple genetic markers. Nucleotide sequence analysis facilitated the reconstruction of phylogenetic relationships. The study also evaluated various potential risk factors, such as clinical status, gender, age, breed, tick infestation, and management practices, to elucidate their associations with TTBPs. Among the cattle cohort, a staggering 87.8% (202/230) tested positive for at least one pathogen. Prevalence statistics encompassed A. marginale (72.2%), T. annulata (68.3%), A. phagocytophilum/A. platys-like complex (66.1%), A. centrale (16.7%), B. bigemina (10.0%), and A. bovis (6.1%). Remarkably, mixed infections involving two, three, and four pathogens were detected in 23%, 52.1%, and 2.2% of animals, respectively. Notably, all asymptomatic cattle were positive for at least one TBP. Tick infestation was observed in 62.2% (143/230) of cattle, predominantly caused by Hyalomma anatolicum (82.5%), Rhipicephalus (Boophilus) annulatus (13.1%), and R. sanguineus sensu lato (4.4%). Risk factors linked to TBPs encompassed tick infestation, older age, and crossbred animals. Clinical presentations among symptomatic cattle encompassed fever, anemia, weight loss, anorexia, jaundice, and enlarged superficial lymph nodes. This study underscores the pivotal role of asymptomatic carriers in the propagation of TTBPs within endemic regions. Furthermore, it emphasizes the potential for the implementation of molecular diagnostics to unmask subclinical infections, thereby affording the opportunity for targeted interventions aimed at ameliorating the burden of TTBPs in resource-constrained smallholder dairy farms.

Antibiotic resistance in tick-borne bacteria: A One Health approach perspective

The emergence and re-emergence of tick-borne bacteria (TBB) as a public health problem raises the uncertainty of antibiotic resistance in these pathogens, which could be dispersed to other pathogens. The impact of global warming has led to the emergence of pathogenic TBB in areas where they were not previously present and is another risk that must be taken into account under the One Health guides. This review aimed to analyze the existing information regarding antibiotic-resistant TBB and antibiotic-resistance genes (ARG) present in the tick microbiome, considering the potential to be transmitted to pathogenic microorganisms. Several Ehrlichia species have been reported to exhibit natural resistance to fluoroquinolones and typhus group Rickettsiae are naturally susceptible to erythromycin. TBB have a lower risk of acquiring ARG due to their natural habitat, but there is still a probability of acquiring them; furthermore, studies of these pathogens are limited. Pathogenic and commensal bacteria coexist within the tick microbiome along with ARGs for antibiotic deactivation, cellular protection, and efflux pumps; these ARGs confer resistance to antibiotics such as aminoglycosides, beta-lactamase, diaminopyrimidines, fluoroquinolones, glycopeptides, sulfonamides, and tetracyclines. Although with low probability, TBB can be a reservoir of ARGs.

Antibacterial properties and in silico modeling perspective of nano ZnO transported oxytetracycline-Zn2+ complex [ZnOTc]+ against oxytetracycline-resistant Aeromonas hydrophila

Emergence of antibiotics resistance has threatening consequences not only for human health but also for animal health issues in agriculture. Several animal pathogenic bacteria have developed antibiotic resistance and managing same has tremendous cost repercussions and may lead to total harvest loss. Hence in the present study, efforts are made to revitalize an old antibiotic molecule, oxytetracycline (OTc), through nanodelivery approaches using zinc oxide nanoparticles (nZnO) to confront OTc resistant fish pathogenic bacteria Aeromonas hydrophila. OTc was impregnated in nZnO through in situ precipitation method to develop OTc loaded ZnO nanoparticles (OTc@nZnO) with average size of 99.42 nm. Spectroscopic investigation of same revealed complexation of Zn²⁺ with amide and aromatic carbonyl moieties of OTc [ZnOTc]⁺. The complex performed better against A. hydrophila with 7-15 mm inhibition zone as compared to nil for bare OTc at same dose. OTc also showed MIC of 150 µg ml^-1 and for OTc@nZnO it was 7.02 µg ml^-1 with faster killing rate (k, -0.95). In silico docking simulation suggest that [ZnOTc]⁺ had low binding affinity (LBE > -5.00 kcal mol^-1) toward TetR(E) and TetA(E) proteins of A. hydrophila as compared to OTc (LBE < -8.00 kcal mol^-1). This study postulates that [ZnOTc]⁺ released from OTc@nZnO can escape TetR(E) and TetA(E) resistance proteins and bind at 30S ribosomal subunit with high affinity (<-11.00 kcal mol^-1) to exert antibacterial properties. In the recent scenario of recurrent antimicrobial resistance, the develop antibiotic-nanocomposites could come out as potential solution, however further study is required for its feasibility for use in animal health care.