Can herd seroprevalence be used as an indicator of enzootic stability for bovine anaplasmosis? Insights from a case-control field study in Brazil.

Bovine anaplasmosis presents a significant challenge to livestock production in tropical, subtropical, and temperate regions. For many years, the concept of enzootic stability/instability (initially established for babesiosis) and herd seroprevalence as an indicator of outbreak risks have been applied to anaplasmosis. However, this model has never been definitively validated for Anaplasma marginale. The objective of this study was to examine the relationship between herd immunity (seroprevalence) and the occurrence of anaplasmosis outbreaks in Southern Brazil. A case-control study was conducted, categorizing farms into two groups: cases (farms with a history of clinical anaplasmosis) and controls (those without anaplasmosis). Thirteen farms were identified as "cases", while 23 were identified as "controls". A substantial difference in seroprevalence distribution between the two groups was observed. The majority of "control" farms exhibited over 75% of animals with antibodies to A. marginale in both calves and heifers, whereas the majority of "case" farms had a seropositive cattle percentage below 75%. Additionally, twelve months after cattle serology tests, we conducted a prospective follow-up survey to identify any clinical cases of anaplasmosis. Statistical associations (P < 0.05) were found between both retrospective and prospective anaplasmosis outbreaks and the hypothetical threshold of herd seroprevalence (75%). We hypothesize that herd seroprevalence may be an indicator of the risk of occurrence of clinical anaplasmosis. It appears that the epidemiology of cattle anaplasmosis, at least in our conditions, aligns with the well-known model of enzootic stability/instability originally applied to bovine babesiosis.

Comparison of Seroprevalence and Identification of Risk Factors for Theileria equi in Horses From Vector-Free and Infested Areas in Southern Brazil.

The apicomplexan hemoprotozoan Theileria equi is a tick-borne pathogen that causes disease in equids, and together with Babesia caballi, causes equine piroplasmosis (EP). Many ticks are associated with EP around the world, and in South America three species may be related: Dermacentor nitens, Amblyomma sculptum, and Rhipicephalus microplus, as they are commonly found in horses. Among the species cited above, only R. microplus is found in Rio Grande do Sul state, Southern Brazil. In addition, this state has the only area legally free of R. microplus in Brazil. This study aimed to compare the seroprevalence for T. equi on farms located in a tick-free area (23 farms, 215 horses) and a tick-infested (25 farms, 141 horses) adjacent areas, as well as to identify potential risk factors for exposure to T. equi. Blood was collected from 356 horses from both areas, and later an indirect enzyme-linked immunosorbent assay was performed to detect anti-T. equi antibodies. Besides the blood collection, questionnaires and interviews were conducted in an attempt to identify potential risk factors. The R. microplus-free zone had 6% seropositive horses against 70% in the tick-infested zone. Previous observation of ticks on horses of the herd increased four times the odds of a horse to be seropositive for T. equi, and by three times if ticks were observed on cattle which share paddocks with horses on the farm. The results showed a large difference in T. equi seroprevalence between tick-infested and free areas, and also emphasized the relevance of R. microplus in the epidemiology of T. equi. The study also reveals the potential of the establishment of a T. equi-free zone for horse breeding in Southern Brazil.

Rotational and selective protocols using acaricides to control a multi-resistant strain of Rhipicephalus microplus under field conditions in Southern Brazil.

The cattle tick, Rhipicephalus microplus, causes severe economic losses to beef and dairy production in several countries. The control of the cattle tick is based mostly on chemical acaricides. Currently, there are reports of tick populations resistant to all six classes of acaricides available on the market. The aim of this work was to evaluate two protocols for the control of the cattle tick, R. microplus, under field conditions. For that, an acaricide rotational-based approach and selective (partial)-based protocols were tested against a multi-resistant tick strain. Eighteen Brangus cattle were divided into three experimental groups: Group 1, a rotational-based approach aiming at six treatments per year (spring-spring period) using four different classes of acaricide (IPV6 protocol); Group 2, a selective (partial) and rotational-based protocol, in which only half of the animals with the highest tick counts were treated (IPV7S protocol); and Group 3 (non-treated). The protocols were able to maintain low tick infestation during the 57 weeks of study. The two experimental groups showed lower tick counts than the non-treated group, but not between them. Weekly efficacy of the experimental protocols reached 95% in Group 1 and 88% in Group 2. Herein, we proposed two protocols of cattle tick control (IPV6 and IPV7S) for use in multi-resistant tick populations in Southern Brazil.

Molecular characterization of bacterial communities of two neotropical tick species (Amblyomma aureolatum and Ornithodoros brasiliensis) using rDNA 16S sequencing.

Ticks are one of the main vectors of pathogens for humans and animals worldwide. However, they harbor non-pathogenic microorganisms that are important for their survival, facilitating both their nutrition and immunity. We investigated the bacterial communities associated with two neotropical tick species of human and veterinary potential health importance from Brazil: Amblyomma aureolatum and Ornithodoros brasiliensis. In A. aureolatum (adult ticks collected from wild canids from Southern Brazil), the predominant bacterial phyla were Proteobacteria (98.68%), Tenericutes (0.70%), Bacteroidetes (0.14%), Actinobacteria (0.13%), and Acidobacteria (0.05%). The predominant genera were Francisella (97.01%), Spiroplasma (0.70%), Wolbachia (0.51%), Candidatus Midichloria (0.25%), and Alkanindiges (0.13%). The predominant phyla in O. brasiliensis (adults, fed and unfed nymphs collected at the environment from Southern Brazil) were Proteobacteria (90.27%), Actinobacteria (7.38%), Firmicutes (0.77%), Bacteroidetes (0.44%), and Planctomycetes (0.22%). The predominant bacterial genera were Coxiella (87.71%), Nocardioides (1.73%), Saccharopolyspora (0.54%), Marmoricola (0.42%), and Staphylococcus (0.40%). Considering the genera with potential importance for human and animal health which can be transmitted by ticks, Coxiella sp. was found in all stages of O. brasiliensis, Francisella sp. in all stages of A. aureolatum and in unfed nymphs of O. brasiliensis, and Rickettsia sp. in females of A. aureolatum from Banhado dos Pachecos (BP) in Viamão municipality, Brazil, and in females and unfed nymphs of O. brasiliensis. These results deepen our understanding of the tick-microbiota relationship in Ixodidae and Argasidae, driving new studies with the focus on the manipulation of tick microbiota to prevent outbreaks of tick-borne diseases in South America.

Investigation of Mycobacterium bovis and Metastrongylus sp. co-infection and its relationship to tuberculosis lesions' occurrence in wild boars.

Animal tuberculosis (aTB) is a zoonotic disease characterized by granulomatous lesions on affected tissues, occurring as a consequence of immunological response to infection. Mycobacterium bovis, the main causative agent of aTB, was investigated in Brazilian wild boars with 37.7 % (29/77) positivity. Among these animals, most had no macroscopic tuberculosis-like lesions (89.6 %; 26/29). The existence of co-infections, which may alter an individual's immune response to an immunological challenge, could influence the formation of tuberculosis lesions. Therefore, we investigated Metastrongylus sp. and aTB co-infection to seek an explanation for the absence of macroscopic lesions in aTB. Of the tested animals, 77.9 % (60/77) had Metastrongylus sp., however, there was no association between its occurrence and the pattern of aTB lesions. The absence of tuberculous lesions in infected animals is worrisome, especially to hunters who handle their carcasses, potentially assuming that the animal is healthy. Studies evaluating other possibilities that can explain the absence of lesions in infected animals should be carried out to better understand these findings.

Resistance to deltamethrin, fipronil and ivermectin in the brown dog tick, Rhipicephalus sanguineus sensu stricto, Latreille (Acari: Ixodidae).

Rhipicephalus sanguineus sensu stricto (s.s.), the temperate lineage of the brown dog tick, is the most common tick found on dogs from urban areas in Rio Grande do Sul (RS) state, southern Brazil. Chemical treatments against ticks are important to control this pest, but can lead to selection for acaricide resistance. Unfortunately, little is known about acaricide resistance in this tick species in Brazil, although such information is very important to companion animal clinical practice. The objective of this study was to analyze acaricide susceptibility of R. sanguineus s.s. from the metropolitan area of Porto Alegre, RS. Engorged females ticks were collected in ten different locations, from naturally infested dogs or the environment (homes, shelters and kennels). The progenies were used in toxicological larval tests with deltamethrin, fipronil and ivermectin. Mortality data was used to determine the median lethal concentrations (LC50) for each tick population and resistance was characterized based on relative susceptibility of the different tick populations against each acaricide. Seven samples were considered resistant to deltamethrin, with resistance ratios (RR) ranging from 2.32 to 5.67. From five tick populations tested with fipronil, three were considered resistant, with RR varying from 2.56 to 13.83. For ivermectin, resistance ratios were lower, ranging from 1.54 to 2.97. The results reveal a notable variance of susceptibility to deltamethrin, fipronil and ivermectin in the R. sanguineus s.s. populations studied. This study documents for the first time the existence of acaricide-resistant populations of R. sanguineus s.s. in Brazil.

Molecular survey of Rickettsia spp. in the Neotropical deer tick Haemaphysalis juxtakochi from Brazilian Pampa.

Spotted fever (SF) is a tick-borne disease associated with Rickettsia spp.. In the Pampa biome, Southern Brazil, cases of SF seem to be strongly linked with the practice of hunting wild animals. An investigation of rickettsiae in tick species found on wild animals could provide more information regarding the rickettsiosis enzootic cycle. The aim of this study is to describe the results of a molecular survey of Rickettsia spp. in the Neotropical deer tick, Haemaphysalis juxtakochi Cooley, 1946 (Acari: Ixodidae), from the Brazilian Pampa. Ticks were obtained from 14 road-killed gray brocket deer, Mazama gouazoubira (Artiodactyla: Cervidae), found in nine different municipalities of Rio Grande do Sul state, Southern Brazil. Ticks were processed individually to obtain genomic DNA, and then Rickettsia spp. was investigated using a set of PCR reactions that amplified the rickettsial fragments of the gltA, ompA, and htrA genes. Of the 24 tick samples tested, DNA of Rickettsia parkeri sensu stricto (s.s.) was found in 11 H. juxtakochi specimens collected in two different areas of the Brazilian Pampa. This is the first report of R. parkeri s.s. (the main agent associated with SF in the Uruguayan, Argentinian, and Brazilian Pampa) in H. juxtakochi ticks. These findings indicate that R. parkeri s.s. may be much more common and widely distributed in the Pampa biome than previously assumed. Moreover, H. juxtakochi ticks and gray brocket deer could participate in the potential spillover of R. parkeri s.s. from endemic to non-endemic areas in the South American Pampa.

Records of ticks on humans in Rio Grande do Sul state, Brazil.

More than seventy tick species have been reported in Brazil. Despite the emergence of tick-borne diseases in Neotropical region, there are still limited data available on tick species parasitizing humans in Brazil. Rio Grande do Sul is the southernmost state of Brazil, comprising the only part of Brazilian territory inside the Pampa biome, as well as the transition between subtropical and temperate zones. Here, we report on human parasitism by ticks in Rio Grande do Sul state between 2004 and 2017. Seventy cases of human parasitism by ticks were recorded, with a total of 81 tick specimens collected. These included 11 tick species belonging to three genera of Ixodidae (hard-ticks), Amblyomma, Haemaphysalis and Rhipicephalus; and one genus of Argasidae, Ornithodoros. The most prevalent tick species associated to cases of human parasitism were Amblyomma parkeri (24%), Rhipicephalus sanguineus sensu lato (22%), Amblyomma aureolatum (15%) and Amblyomma ovale (12%). A spatial analysis showed two major hot spots of human parasitism by ticks in Rio Grande do Sul state. The findings of this study highlight the need for permanent monitoring of human parasitism by ticks in order to provide a better understanding of tick and tick-borne disease eco-epidemiology, and the early identification of potential cases of tick-borne diseases, particularly in spotted fever endemic regions.

Imidocarb dipropionate in the treatment of Anaplasma marginale in cattle: Effects on enzymes of the antioxidant, cholinergic, and adenosinergic systems.

Anaplasmosis is a worldwide hemolytic disease in cattle caused by a gram-negative obligatory intracellular bacterium, characterized by anemia and jaundice. Among the treatments used for anaplasmosis is a drug called imidocarb dipropionate, also indicated as an immunomodulator agent. However, it causes side effects associated with increased levels of acetylcholine. In view of this, the effects of imidocarb dipropionate on the purinergic system, and antioxidant enzymes in animals naturally infected by Anaplasma marginale were evaluated. Young cattle (n = 22) infected by A. marginale were divided into two groups: the Group A consisted of 11 animals used as controls; and the Group B composed of 11 animals. Imidocarb dipropionate (5 mg/kg) was used subcutaneously to treat both groups (the Group A on day 6 and the Group B on day 0). The treatment reduced acetylcholinesterase (AChE), and adenosine deaminase (ADA) activities, and increased the dismutase superoxide and catalase activities. No changes on lipid peroxidation (TBARS levels) and BChE activities were noticed. These results suggest that imidocarb dipropionate used to treat A. marginale infection in cattle has effect on antioxidant enzymes, and significantly inhibits the enzymatic activities of ADA and AChE.

Cholinesterases as markers of the inflammatory process associated oxidative stress in cattle infected by Babesia bigemina.

The objective of this study was to assess the influence of an asymptomatic experimental infection by Babesia bigemina on cholinesterase's as markers of the inflammatory process and biomarkers of oxidative imbalance. For this purpose, eight naive animals were used, as follows: four as controls or uninfected; and four infected with an attenuated strain of B. bigemina. Blood samples were collected on days 0, 7 and 11 post-inoculation (PI). Parasitemia was determined by blood smear evaluation, showing that the infection by B. bigemina resulted in mean 0.725 and 0.025% on day 7 and 11 PI, respectively, as well as mild anemia. The activities of acetylcholinesterase, butyrylcholinesterase and catalase were lower, while levels of thiobarbituric acid reactive substances and superoxide dismutase activity were higher in infected animals, when compared with the control group. This attenuated strain of B. bigemina induced an oxidative stress condition, as well as it reduces the cholinesterasés activity in infected and asymptomatic cattle. Therefore, this decrease of cholinesterase in infection by B. bigemina purpose is to inhibit inflammation, for thereby increasing acetylcholine levels, potent anti-inflammatory molecules.

Cattle experimentally infected by Anaplasma marginale: Influence of splenectomy on disease pathogenesis, oxidative profile, and antioxidant status.

Bovine anaplasmosis is caused by the obligate intraerythrocytic bacteria Anaplasma marginale. These bacteria are transmitted by tick species such as Rhipicephalus (Boophilus) microplus, blood-sucking insects, and fomites (needles, clippers, and other blood contaminated equipment). During the acute phase of infection, animals may develop fever, anemia, jaundice, and hepatosplenomegaly. The aims of this study are to quantify the bacteremia by quantitative PCR in eight naïve calves experimentally infected by A. marginale [splenectomized (n = 4), and intact/non-splenectomized (n = 4)], and to correlate these findings with markers of oxidative stress on days 0, 8, 15, 21 and 23 post-infection. Complete blood counts (CBC) were performed in both groups. Lipid peroxidation was estimated by quantifying thiobarbituric acid reactive substances (TBARS); and non-enzymatic antioxidants were assessed by erythrocyte content of non-protein thiols (NPSH). There were no significant differences in complete blood counts (CBC) between the two groups. However, both groups had a slight decrease on packet cell volume (PCV), erythrocytes and hemoglobin concentration, as well as an increase in total leukocyte counts due to elevated lymphocytes when comparing pre and post-infection with A. marginale. Progressive increase on TBARS levels and concomitant decrease on NPSH content were observed in all animals, without significant differences between splenectomized and intact animals. A positive correlation between bacteremia and TBARS, and a negative correlation between bacteremia and NPSH were observed in both groups with higher correlation for NPSH in splenectomized animals. A negative correlation between TBARS and NPSH levels was observed in both groups indicating lipid peroxidation without a non-enzymatic antioxidant response. The results of experimental infection by A. marginale in cattle showed that bacteremia has an impact on lipid peroxidation regardless of the splenectomy.

Influence of experimental Anaplasma marginale infection and splenectomy on NTPDase and 5'nucleotidase activities in platelets of cattle.

The objective of this paper was to evaluate NTPDase and 5'-nucleotidase activities in platelets of bovine with and without spleen and infected by Anaplasma marginale. Our results demonstrate that infection along with splenectomy is able of inducing a profile of cellular protection, which showed an increase in the degradation of the nucleotides ATP and ADP by NTPDase, in addition to AMP by 5'nucleotidase to form the nucleoside adenosine in platelets, i.e., the enzymatic activities of platelets were increased in splenectomized animals when compared to non-splenectomized group. It notes that adenosine is a molecule with anti-inflammatory function. But this profile is related to a deficiency in immune signaling triggered by nucleotide ATP, which may be related to the increase in bacteremia and disability in combating the parasite in splenectomized host.

Diminazene aceturate liposomes: morphometric and biochemical liver, kidney, and spleen of rats infected with Trypanosoma evansi.

The aim of this study was to evaluate the effect of treatment with liposomal (L-DMZ) and conventional (C-DMZ) diminazene aceturate formulations on hepatic and renal functions of rats, experimentally infected with Trypanosoma evansi. For this purpose, 72 Wistar rats (Rattus norvegicus) were divided into six groups (A, B, C, D, E, and F). Each group was subdivided into two other subgroups in order to assess the biochemical and histological results on days 7 and 40 post-treatment (PT). Treatments were carried out based on two different therapeutic protocols: L-DMZ and C-DMZ at 3.5mg/kg(-1), single dose (groups C and D), and five successive doses within intervals of 24h (groups E and F). Groups A and B corresponded to uninfected and infected (without treatment) animals, respectively. Sample collections were held on days 7 and 40 PT for the assessment of hepatic [alkaline phosphatase (AP), alanine transferase (ALT), albumin, gamma glutamil transferase (GGT) and renal functions (creatinine and urea). Additionally, the histology of fragments of liver, kidney, and spleen was performed. Animals in group B showed a significant increase in AP, GGT, ALT, and urea when compared with group A. On day 7 post-inoculation (PI), the biochemical analysis showed a reduction (P<0.05) of AP and GGT, while the levels of urea were increased in groups C, D, E, F. On day 40 PT, ALT was increased in these same groups when compared with group A. In histopathology, changes in liver samples were observed on day 7 PT in groups D and F, especially regarding the area and density of the hepatocytes. Renal analysis exhibited changes in glomerular space, glomerular, and corpuscular areas in group E. Therefore, these results allowed us to conclude that the treatment with L-DMZ and C-DMZ led to variable biochemical changes, which defined the functions of the liver and kidneys of treated animals, since the main histopathology alterations were observed in animals treated with liposomes, at their higher dosages. Thus, treatments with L-DMZ and C-DMZ in five consecutive doses were effective although being followed by liver toxicity.

Ticks (Acari: Ixodidae) from yellow armadillo, Euphractus sexcinctus (Cingulata: Dasypodidae), in Brazil's Pantanal wetlands.

Tick species parasitizing yellow armadillo, Euphractus sexcinctus, were recorded from October 2006 to October 2007 in Pantanal. A total of 89 ticks were collected from 23 yellow armadillos. Most ticks (n=50) were identified as Amblyomma cajennense (Fabricius) (32 males and 18 females). The only other species found was Amblyomma parvum (Aragão) (three females and two males). The remaining ticks were immatures of Amblyomma (29 nymphs and five larvae). The prevalence of A. cajennense was 55%, the mean intensity was 2.7±0.5 (SE) (n=17) and the mean abundance was 1.5±0.4 (n=31).

Amblyomma aureolatum (Acari: Ixodidae) parasitizing margay (Leopardus wiedii) in Rio Grande do Sul.

We report the finding of Amblyomma aureolatum (Acari: Ixodidae) parasitizing margay (Leopardus wiedii) in the locality of Gravataí (29° 47' 12.9" S and 50° 53' 44.1" W; 241 m alt.), State of Rio Grande do Sul, Southern Brazil. This is the first report of this species of Ixodidae on margay in Southern Brazil. This finding indicates an increased number of hosts for this tick species.

Ticks (Acari: Ixodidae) from yellow armadillo, Euphractus sexcinctus (Cingulata: Dasypodidae), in Brazil's Pantanal wetlands

Tick species parasitizing yellow armadillo, Euphractus sexcinctus, were recorded from October 2006 to October 2007 in Pantanal. A total of 89 ticks were collected from 23 yellow armadillos. Most ticks (n = 50) were identified as Amblyomma cajennense (Fabricius) (32 males and 18 females). The only other species found was Amblyomma parvum (Aragão) (three females and two males). The remaining ticks were immatures of Amblyomma (29 nymphs and five larvae). The prevalence of A. cajennense was 55 percent, the mean intensity was 2.7 ± 0.5 (SE) (n = 17) and the mean abundance was 1.5 ± 0.4 (n = 31).

Amblyomma aureolatum (Acari: Ixodidae) parasitizing margay (Leopardus wiedii) in Rio Grande do Sul / Amblyomma aureolatum (Acari: Ixodidae) parasitando Gato-Maracajá (Leopardus wiedii) no Rio Grande do Sul

We report the finding of Amblyomma aureolatum (Acari: Ixodidae) parasitizing margay (Leopardus wiedii) in the locality of Gravataí (29º 47' 12.9'' S and 50º 53' 44.1'' W; 241 m alt.), State of Rio Grande do Sul, Southern Brazil. This is the first report of this species of Ixodidae on margay in Southern Brazil. This finding indicates an increased number of hosts for this tick species.

Foi registrado o encontro de Amblyomma aureolatum (Acari: Ixodidae) em gato-maracajá (Leopardus wiedii), na localidade de Gravataí (29º 47' 12,9'' S and 50º 53' 44,1'' O; 241 m alt.), região metropolitana de Porto Alegre, Rio Grande do Sul. Esse é o primeiro registro desse ixodídeo parasitando essa espécie de felídeo e amplia a distribuição de hospedeiros no estado.

Tripanosomatides like Trypanosoma theileri in the cattle tick Boophilus microplus.

Findings of epimastigotes forms of a tripanosomatide is reported in the hemolymph of the cattle tick Boophilus microplus in the state of Rio Grande do Sul, southern Brazil. Morphological evidences suggest they are similar to Trypanosoma theileri, a species described as non pathogenic to cattle, and usually transmitted by tabanids.

Tripanosomatides like Trypanosoma theileri in the cattle tick Boophilus microplus / Tripanosomatídeos similares a Trypanosoma theileri no carrapato dos bovinos Boophilus microplus

Findings of epimastigotes forms of a tripanosomatide is reported in the hemolymph of the cattle tick Boophilus microplus in the state of Rio Grande do Sul, southern Brazil. Morphological evidences suggest they are similar to Trypanosoma theileri, a species described as non pathogenic to cattle, and usually transmitted by tabanids.

Descreve-se a ocorrência de formas epimastigotas de um tripanosomatideo na hemolinfa do carrapato do bovino Boophilus microplus no Estado do Rio Grande do Sul. Evidências morfológicas sugerem tratar-se de Trypanosoma theileri , espécie descrita como não patogênica aos bovinos e que usualmente é transmitida por tabanídeos.

[Haemaphysalis juxtakochi Cooley, 1946 (Acari: Ixodidae) parasitizing Mazama nana (Hensel, 1872) (Artiodactyla: Cervidae) in the State of Rio Grande do Sul]. / Haemaphysalis juxtakochi Cooley, 1946 (Acari: Ixodidae) parasitando Mazama nana (Hensel, 1872) (Artiodactyla: Cervidae) no Estado do Rio Grande do Sul.

The record of Haemaphysalis juxtakochi Cooley, an ixodid tick, on the brocket deer, Mazama nana (Hensel), represents a new report after 34 years of its last report in the State of Rio Grande do Sul. The tick specimens (three males and one female) were found in Cachoeira do Sul, RS (30 degrees 02'21''S, 52 degrees 53'38''W). This place is elevated 72 m sea above, with an annual average temperature of 18.8 degrees C, and annual average rainfall of 1.438 mm. This is the first record of this tick species in a Cervidae and it is the second occurrence report for the State of Rio Grande do Sul.