Abstract
Brucellosis is a severe public health problem in the Inner Mongolia regions of China. The recent prevalence of brucellosis outbreaks may be attributed to an increase in the activity of ticks and other air-borne vectors. Dermacentor nuttalli (D. nuttalli) is a native tick species of Inner Mongolia; similar to other tick species, D. nuttalli carries a variety of pathogens that can be transmitted to a wide range of animals. In this study, we have investigated the potential of D. nuttalli in transmitting brucellosis. From 2015 to 2019, 2,256 ticks were collected from 23 different pastoral areas of Hulun Buir. Brucellosis pathogen was detected using DNA extracted from different developmental stages of ticks. Salivary gland and midgut tissue samples were used as templates to amplify Brucella Bscp31 gene (Brucella genus-specific gene) by using TaqMan Real-Time polymerase chain reaction (PCR). To detect the presence of Bscp31 protein, which is specific to Brucella spp., in the midgut and salivary gland tissues of D. nuttalli, Western blotting and immunofluorescence were performed. Additionally, Brucella spp. were isolated using a culture medium. Tick samples were identified as D. nuttalli. Different percentages of Brucella genus-specific genes could be found in the tick samples. From 2015 to 2019, the positivity rate for the detection of Bscp31 gene in D. nuttalli ranged from 0.00 to 87.80%, with the highest rate of 89.00%. In addition, Brucella genus-specific genes were successfully detected in the samples isolated from all the developmental stages and anatomical regions of ticks. Bscp31 protein was present in the midgut and salivary gland of D. nuttalli. Further, B. melitensis biotype 3 was isolated from eggs and engorged adults of D. nuttalli. These findings demonstrate that D. nuttalli is a potent, long-term carrier of Brucella spp. that can exhibit transovarial transmission potential, presenting D. nuttalli as a novel arthropod host for Brucella spp. This study, therefore, indicates the potential risk of transmission of brucellosis via tick bites among animals as well as human beings.
Highlights
Brucellosis, a zoonotic infectious disease caused by Brucella spp., was once distributed worldwide [1]; China effectively curbed it using attenuated vaccines in the 1980s [2, 3]
The genus of Brucella can be divided into six species according to their biotypes, namely, B. abortus, B. melitensis, B. ovis, B. canis, B. suis, and B. neotomae
Detection of Brucella Genus-Specific Genes in Tick Samples Details of the Brucella genus-specific genes detected in ticks collected during 2015–2019 are presented in Supplementary Table 1
Summary
Brucellosis, a zoonotic infectious disease caused by Brucella spp., was once distributed worldwide [1]; China effectively curbed it using attenuated vaccines in the 1980s [2, 3]. There have been reports of outbreaks of human brucellosis especially in Inner Mongolia [4] This disease poses serious problems against the healthy development of animal husbandry-associated economy and leads to the development of issues of social and public security [5, 6]. Inner Mongolia has arid and semi-arid grassland type climate, but the global climate changes have impacted the inherent climatic characteristics of these areas [7]. These climatic changes may have led to an alteration in vector-pathogen interactions and in turn created favorable conditions for the prevalence of certain infectious diseases [8]. It is worth noting that a rapid increase in the numbers of some common arthropods (such as mosquitoes, ticks, and flies) in the grasslands has occurred with the change in climate, which may be a probable reason behind the increase in the incidence of insect-transmitted diseases in these areas [12]
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