Current challenges of the management and epidemiology of bovine anaplasmosis

Abstract

Bovine anaplasmosis, caused by the intracellular rickettsia Anaplasma marginale, is endemic in several areas of the United States and has continued to impact cattle production. While considerable research has been done over the past several decades, control strategies for anaplasmosis have advanced minimally since the first anaplasmosis vaccine was marketed in the US in the 1960s. However, these research findings have continued to contribute to our overall understanding of the complexity of bovine anaplasmosis. With the advent of molecular biology, host/pathogen interactions are currently better defined and the classification of Anaplasma has been reorganized to include several organisms in addition to those that are host-specific for ruminants. In this review, the current status of anaplasmosis is discussed with the aim of providing insight to bovine practitioners on the future challenges for the management, diagnosis, and control of bovine anaplasmosis. This review focuses on updated information on the classification of the genus Anaplasma and related organisms, the developmental cycle of A. marginale in cattle and ticks, the role of male ticks in transmission of anaplasmosis, the diversity of A. marginale strains, the wildlife reservoirs of A. marginale, and the potential influence of climate change on the epidemiology of this serious disease. A second review will follow which focuses on current issues related to diagnosis and control of bovine anaplasmosis. Overall, the goal of these reviews is to provide an understanding of the current status of research and knowledge of bovine anaplasmosis and provide veterinarians answers to frequently asked questions.

Revisão sistemática sobre diagnóstico molecular da tristeza parasitária bovina no Brasil: ocorrência e oportunidades futuras

“…One gap identified from the analysis of the studies presented here concerns the quantification of production losses due to infections by agents such as A. marginale and Babesia spp. Researchers commonly note significant losses for producers resulting from disease, the need for treatment, abortions, and animal deaths (Kocan et al, 2010). However, none of the studies reviewed aimed to assess the damage caused by the presence or intensity of infection in the evaluated herds.…”

Association between chronic Anaplasma marginale and Babesia spp. infection and hematological parameters of taurine heifers

“…Although most of Brazil is considered endemic for TF agents, there are several areas of enzootic instability in the state of Rio Grande do Sul (Santos et al, 2019). Thus, persistently infected animals, identified through molecular techniques, are at risk of increased parasitemia and recurrence of acute infection, thus increasing the economic losses (Kocan et al, 2010). Pregnant females are at higher risk, considering that these parasites can be transmitted to the fetus, thus causing pregnancy loss and stillbirth (Henker et al, 2020).…”

“…Its occurrence is directly related to the distribution of the cattle tick, Rhipicephalus (Boophilus) microplus, and its estimated economic impact in Brazil is US$ 3.24 billion, attributable to production losses (Grisi et al, 2014). Although R. microplus is the primary vector for these agents, tabanids and iatrogenic transmission may also be responsible for transmission of this disease (Kocan et al, 2010;Palmer & Clothier, 2015;Zaugg, 2015). Animals from tick-free or enzootic instability areas are highly susceptible to these infections and have high morbidity rates, presenting anemia, fever, jaundice, and weight loss, and even culminating in death (Kocan et al, 2010).…”

“…Although R. microplus is the primary vector for these agents, tabanids and iatrogenic transmission may also be responsible for transmission of this disease (Kocan et al, 2010;Palmer & Clothier, 2015;Zaugg, 2015). Animals from tick-free or enzootic instability areas are highly susceptible to these infections and have high morbidity rates, presenting anemia, fever, jaundice, and weight loss, and even culminating in death (Kocan et al, 2010). Also, it is known that severe anemia caused by TF results in hypoxia, which can lead to tissue hypoxia and subsequent abortion (Givens & Marley, 2008).…”

“…and A. marginale directly affects fetal organs, causing splenomegaly, hemorrhages, and neurological damage, and resulting in fetal loss, stillbirth, and neonatal death (Costa et al, 2016;Henker et al, 2020). Animals recovering from the acute phase of TF remain persistently infected, with low levels of parasitemia, thus perpetuating the presence of infectious agents in the herd (Kocan et al, 2010).…”