Epidemiology of Ornithodoros brasiliensis (mouro tick) in the southern Brazilian highlands and the description of human and animal retrospective cases of tick parasitism

Instituto de Pesquisas Veterinárias Desidério Finamor (IPVDF), Fundação Estadual de Pesquisa Agropecuária (FEPAGRO), Eldorado do Sul, RS, Brazil. Electronic address: .
Ticks and Tick-borne Diseases (Impact Factor: 2.72). 12/2012; 4(1-2). DOI: 10.1016/j.ttbdis.2012.09.004
Source: PubMed


Ornithodoros brasiliensis, also known as the "mouro" tick, is an argasid tick found exclusively in the southern Brazilian highlands. O. brasiliensis parasitism is frequently associated with severe symptoms directly induced by the tick bite, a condition compatible with the definition of tick toxicosis. The objectives of this work include (i) the determination of the distribution of O. brasiliensis in farms located in the tick-endemic region, (ii) the description of the characteristics of O. brasiliensis habitats, (iii) the analysis of risk factors associated with O. brasiliensis, and (iv) the retrospective description of cases of human and animal parasitism by O. brasiliensis. Of the 30 farms included in this study, O. brasiliensis was identified on 5 farms (frequency 16.7%), in which several ticks found in high density buried in soil were collected. Information regarding the tick habitats and the local population was recorded. The data indicated that O. brasiliensis feeds on humans, dogs, armadillos (Dasypus hybridus), and possibly skunks (Conepatus chinga). The analysis of risk factors indicated that the presence of house basements with an unpaved (natural soil) floor on farms and insufficient sanitary conditions significantly enhanced the probability of identifying O. brasiliensis. Additionally, we describe retrospectively cases of tick parasitism in 28 humans and 11 dogs including the most common symptoms associated with tick toxicosis. This is the first study concerning O. brasiliensis epidemiology, distribution, and habitat, and the report represents the most comprehensive characterization of Ornithodoros bite-associated toxicosis syndrome.

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    • "Symptoms of general toxicoses were also reported after soft tick bites that include pain, blisters, local irritation, oedema, fever, pruritus, inflammation and systemic disturbances [25]. Recently, human and canine toxicoses induced by the argasid tick O. brasiliensis, known as “mouro” tick, were reported and the most frequent symptoms of toxicoses induced by this tick species were local pruritus, slow healing lesions, local edema and erythema, and local skin rash [26]. Different types of immune reactions can also be included in the general scope of tick toxicoses [3,27]. "
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    ABSTRACT: Introduction As an ecological adaptation venoms have evolved independently in several species of Metazoa. As haematophagous arthropods ticks are mainly considered as ectoparasites due to directly feeding on the skin of animal hosts. Ticks are of major importance since they serve as vectors for several diseases affecting humans and livestock animals. Ticks are rarely considered as venomous animals despite that tick saliva contains several protein families present in venomous taxa and that many Ixodida genera can induce paralysis and other types of toxicoses. Tick saliva was previously proposed as a special kind of venom since tick venom is used for blood feeding that counteracts host defense mechanisms. As a result, the present study provides evidence to reconsider the venomous properties of tick saliva. Results Based on our extensive literature mining and in silico research, we demonstrate that ticks share several similarities with other venomous taxa. Many tick salivary protein families and their previously described functions are homologous to proteins found in scorpion, spider, snake, platypus and bee venoms. This infers that there is a structural and functional convergence between several molecular components in tick saliva and the venoms from other recognized venomous taxa. We also highlight the fact that the immune response against tick saliva and venoms (from recognized venomous taxa) are both dominated by an allergic immunity background. Furthermore, by comparing the major molecular components of human saliva, as an example of a non-venomous animal, with that of ticks we find evidence that ticks resemble more venomous than non-venomous animals. Finally, we introduce our considerations regarding the evolution of venoms in Arachnida. Conclusions Taking into account the composition of tick saliva, the venomous functions that ticks have while interacting with their hosts, and the distinguishable differences between human (non-venomous) and tick salivary proteins, we consider that ticks should be referred to as venomous ectoparasites.
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    • "Algunos autores afirman que las picaduras de ciertas especies de este género son en extremo dolorosas , ocasionando ampollas, inflamación e incluso fuertes reacciones alérgicas y choques anafilácticos [3] [5] [6]. "
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    ABSTRACT: Ornithodoros brasiliensis is a nidicolous tick only found in the southern Brazilian highlands region. O. brasiliensis parasitism is frequently associated with toxicosis syndrome, which can lead to severe reactions, ranging from local pruritus and pain to systemic disturbances both in humans and dogs. One of the most frequent findings associated with an O. brasiliensis bite is a slow healing lesion at the site of tick attachment, which can take several weeks to heal. This work tested the hypothesis that an O. brasiliensis salivary gland homogenate is able to modulate the skin wound-healing process in vivo, using a model of excisional skin lesion in rats, which are divided into two groups: (1) control group and (2) treated group, which topically received salivary gland homogenate equivalent to the protein amount of one whole salivary gland (≈5 μg protein). The hypothesis that O. brasiliensis salivary gland homogenates interfere with endothelial cell proliferation, a key role phenomenon in wound healing, was also tested. O. brasiliensis salivary gland homogenates significantly delay skin wound healing. The time to full healing of skin lesions in control rats was 15 days, contrasting with 24 days in rats topically treated with O. brasiliensis salivary gland homogenates. The calculated HT(50) (healing time to recover 50 % of the wound area) for control groups was 3.6 days (95 % CI, 3.2-3.9) and for salivary gland treated rats was 7.7 days (95 % CI, 7.0-8.4). Salivary gland homogenates have a strong cytotoxic activity on cultured endothelial cells (LC(50), 13.6 mg/ml). Also, at sublethal concentrations (≤3 mg/ml), salivary gland homogenates have a remarkable anti-proliferative activity (IC(50) 0.7 mg/ml) on endothelial cells, equivalent to ≈0.03 salivary gland pairs, an activity which seems to be much greater than reported for any other tick species. This is the first report about the biological activities of O. brasiliensis salivary compounds and provides the first in vivo evidence to support the concept of wound-healing modulation by tick salivary secretions. Results shown here contribute to an understanding of O. brasiliensis tick toxicosis syndrome, and also increase our knowledge of tick salivary bioactive compounds.
    Full-text · Article · Feb 2013 · Parasitology Research
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