Ticks and tick-borne diseases of bovines in Pakistan

Abstract

Ticks and tick-borne diseases (TTBDs) impact the health and production of livestock in tropical and subtropical countries, such as Pakistan, where the majority of the rural population is dependent upon production animals for their livelihood. Several tick species are known to infest bovines in Pakistan, and can transmit various tick-borne diseases (TBDs), including anaplasmosis, babesiosis and theileriosis. Despite the substantial adverse socioeconomic impact of TTBDs, little is known about the epidemiology of these diseases in Pakistan. This thesis – comprising six chapters – aimed at investigating some key epidemiological aspects of TTBDs in bovines from different agro-ecological zones (AEZs) of Pakistan. In Chapter 2, a participatory epidemiological (PE) study was conducted to investigate the major bovine health and production (BH&P) constraints in five AEZs of Pakistan. The findings revealed that TTBDs were among the major BH&P constraints, according to both farmers as well as animal-health professionals (AHPs). Besides providing an insight into the farmers’ knowledge about BH&P constraints, this study identified important knowledge gaps among farmers about risk factors and modes of transmission of major infectious disease constraints, including TBDs. This study led to subsequent epidemiological investigations of TTBDs of bovines in Pakistan using molecular methods. In Chapter 3, morphological and molecular tools were applied in a cross-sectional investigation of bovine ticks from five AEZs of Pakistan. Results revealed a high tick prevalence (46.1%) both in cattle (Bos indicus and Bos taurus) and water buffaloes (Bubalus bubalis); the five tick species identified belonged to two genera, Hyalomma and Rhipicephalus, with Hyalomma (Hy.) anatolicum – a known vector of a zoonotic disease, Crimean-Congo haemorrhagic fever – have the highest prevalence. This study provided the first genetic characterisation of Rhipicephalus annulatus and Hy. hussaini from cattle in the Indian subcontinent. The findings of this study highlighted the need to conduct large-scale epidemiological investigations of TBPs in both ticks and bovine populations. In Chapter 4, the use of a novel, microfluidic real-time PCR revealed a high prevalence of 12 potentially pathogenic and two endosymbiotic microorganisms in ticks of bovines from five AEZs of Pakistan. This study demonstrated the presence of mixed infections with up to five microorganisms in a single tick. Additionally, it provided the first evidence of the occurrence of several novel and potentially zoonotic pathogens in ticks in Pakistan. Furthermore, ticks from cattle had a higher prevalence of TBPs than those from buffaloes. Similarly, prevalence rates of TBPs in ticks varied among different age groups of bovines. These findings illustrated the advantages of using the novel microfluidic tool for epidemiological investigations of TBDs. Overall, this thesis has significantly advanced the knowledge of TTBDs of bovines in Pakistan and emphasises the need for further, intensive research on the epidemiology, ecology and population genomics of TTBPs. It also highlights the advantages of using advanced molecular tools to gain deep insights into interactions among vector, microbiome, mammalian host and the environment in the near future. Such insights should contribute toward designing improved methods for the integrated control of TTBDs in Pakistan and elsewhere.