The link between Acaricide usage and Oxytetracycline resistance genes in Anaplasma marginale infected cattle blood from selected farms in Kyenjojo, Kumi and Serere Districts

Abstract

The management of Bovine Anaplasmosis relies on vector control and chemotherapy. Following the rise of acaricide resistance in Uganda, there is an increase in TBDs incidence, resulting into over reliance on antimicrobials to treat infected animals. Oxytetracycline, being cheap, effective with minimal adverse effects, is mostly used in treating Anaplasmosis. This study was conducted on selected farms in Kyenjojo, Kumi and Serere districts, where resistance in Boophilus decoloratus had been previously reported. The study aimed at investigating otrA and otrB resistance genes in A. marginale infected cattle and access their association with acaricide usage. DNA was extracted from 316 cattle blood samples and screened for msp4 gene. A. marginale positive samples were screened for otrA and otrB using in house primers, and representative samples sequenced using Oxford Nanopore to confirm the PCR product. Six out of the Eight farmers (6/8) in Kyenjojo reported to have used more than one acaricide in the last six months. The proportion of A. marginale was 70% (140/200) and 35.3% (41/116) in Kyenjojo and Kumi/Serere farms respectively. The difference in the frequency of A. marginale between Kyenjojo and Kumi/Serere was statistically significant (P=<0.001). The general proportion of otrA and otrB among the 181 A. marginale infected cattle was 71.8% (130/180) and 47.8% (86/180) respectively. Among Kyenjojo sampled animals, otrA and otrB proportion was 68.6% and 44.3% respectively, while in Kumi & Serere animals, otrA and otrB proportion was 82.9% and 58.5% respectively. Multivariate regression revealed that Exotic breeds were 1.89 times more likely to have otrA compared to local breeds (OR=1.89, 95%CI=0.85-4.40, p=0.13). No acaricide usage factor had a significant relationship with otrA, despite the higher proportions of otrA observed among animals from farms that rotated acaricides due to presence of a new product on market (77.3%), randomly changed acaricides on observing resistance (75.2%) and those that sprayed every week (71.8%). Sequence analysis revealed a 50-55% similarity with sequences available in the database, with study sequences clustering together. This study reveals high proportions of OTC resistance genes in A. marginale infected cattle blood. Animals from farms with poor acaricide use practices had higher proportions of otrA. Larger studies involving more farms and culturing of A. marginale would provide stronger statistical power to define acaricide usage association with OTC resistance as well as assessing invitro anti-microbial resistance profiles.