Recent Advances in the Immunologic Method Applied to Tick-Borne Diseases in Brazil

Abstract

Zoonotic-origin infectious diseases are one of the major concerns of human and veterinary health systems. Ticks, as vectors of several zoonotic diseases, are ranked second only to mosquitoes as vectors. Many ticks' transmitted infections are still endemic in the Americas, Europe, and Africa and represent approximately 17% of their infectious diseases population. Although our scientific capacity to identify and diagnose diseases is increasing, it remains a challenge in the case of tick-borne conditions. For example, in 2017, 160 cases of the Brazilian Spotted Fever (BSF, a tick-borne illness) were confirmed, alarming the notifiable diseases information system. Conversely, Brazilian borreliosis and ehrlichiosis do not require notification. Still, an increasing number of cases in humans and dogs have been reported in southeast and northeastern Brazil. Immunological methods applied to human and dog tick-borne diseases (TBD) show low sensitivity and specificity, cross-reactions, and false IgM positivity. Thus, the diagnosis and management of TBD are hampered by the personal tools and indirect markers used. Therefore, specific and rapid methods urgently need to be developed to diagnose the various types of tick-borne bacterial diseases. This review presents a brief historical perspective on the evolution of serological assays and recent advances in diagnostic tests for TBD (ehrlichiosis, BSF, and borreliosis) in humans and dogs, mainly applied in Brazil. Additionally, this review covers the emerging technologies available in diagnosing TBD, including biosensors, and discusses their potential for future use as gold standards in diagnosing these diseases.

Keywords: Brazilian Spotted Fever; Lyme disease; biosensors; borreliosis; ehrlichiosis; immunologic diagnosis; serological diagnosis; tick-borne diseases.

Figure 1

Tick disease transmission life cycle (Rickettsia, Ehrlichia, Borrelia, and others) in Brazil. Horses and capybara are part of the tick cycle in Brazil. However, it is essential to understand that each tick may be associated with transmitting more than one pathogen.

Figure 2

Number of cases of Brazilian Spotted Fever in the period 2007–2021 in Brazil [23]. * p < 0.05.

Figure 3

Evidence of the immune response to rickettsiosis, ehrlichiosis, and borreliosis. The IgM response can be detected in the first days with a major peak in the first three weeks, while IgG is seen between the first and second week and can persist for a long time, depending on the disease.