Seasonal dynamics of Anocentor nitens on horses in Brazil

Anocentor nitens is a widespread ectoparasite of horses in Brazil. A study of the seasonal dynamics of the parasitic phase of this tick was made by regular census of engorging females (>/=4mm) on free-ranging horses, fortnightly from July 1995 to July 1997, at Pedro Leopoldo, Minas Gerais. Twenty horses were divided into four groups of five animals per group, each having a similar mix of resistant and less resistant animals, based on initial infestation. Every 2 weeks, one of the groups, in sequence, was treated with an acaricide to prevent excessive infestations, and female ticks were censused 38 days later. The acaricide dips did not interfere with the seasonal dynamics of the tick population, which produced three major peaks of activity over a 12-month period. The first two peaks were in the hot, wet season and the third in the cold dry season. Tick numbers were similar for the two 12-month periods, decreasing from the spring and summer to the autumn and winter. Infestation rates were not equal among different horses. Twenty percent of the horses were responsible for 48% of the total parasite load, while 30% accounted for only 2.5% of the total parasite load. Principal predilection sites were; the ear (61%), mane (21%), and muzzle and face (6%). Measures for the strategic control of A. nitens ticks are discussed.     

Population dynamics of the free-living stages of Amblyomma cajennense (Fabricius, 1787) (Acari: ixodidae) on pastures of Pedro Leopoldo, Minas Gerais State, Brazil

A study on the population behavior of Amblyomma cajennense larvae, nymphs and adult free-living stages was carried out in Pedro Leopoldo County, Minas Gerais State, Brazil, from July 1995 to July 1997. Larvae were collected from pasture from April to October using the technique of drag sampling with flannelette. The maximal larval population was observed during autumn (May) representing, respectively, 48 and 82% of the total numbers recovered during the first and the second years of the experiment. Nymphs and adults were captured throughout the year by the use of traps with carbon dioxide as chemical attractant. The highest population of nymphs occurred during the winter (July), representing 39.5% of the total collected specimens. Adults had the highest population density on pasture during spring and summer, i.e., from August to May, with peaks in January and February, representing 46 and 38.3% of the total collected specimens during the first and the second year of study, respectively.     

Parasitic phase of Anocentor nitens (Acarina: Ixodidae) in cattle

The parasitic phase of Anocentor nitens (Neumann) in cattle was studied. Larval stage was present up to 15 days post-infestation (p.i.), concomitant with nymphae from day 8 p.i. Nymphae were observed up to day 23 p.i., adults being seen from day 15 p.i. onwards. Male ticks disclosed active movements from day 17 p.i. and detachment of engorged females began 22 to 24 days p.i. Massive detachment occurred from day 28 p.i. Preferential sites of parasitic stages were ear and neck (lateral side).     

Epidemiological Aspects of Babesia equi in Horses in Minas Gerais,Brazil

The prevalence of Babesia equi in two climatic regions of Minas Gerais state was determined using the indirect fluorescent antibody test (IFAT) with blood samples obtained from horses in two slaughterhouses. Of 399 samples, 241 (60.4%) showed a positive reaction. Anti-B. equi antibody was detected in every county studied, the prevalence being 59.7% for horses in the area where the temperature rises above 18°C in winter and 61.4% in the area where it remains below 18°C, indicating that climatic variation has no substantial effect on the prevalence of the infection in Brazil. Blood samples collected from all 95 horses on a ranch in the state of Minas Gerais, Brazil, on which clinical babesiosis had never been reported, were subjected to the IFAT. Anti-B. equi antibodies were detected in horses of all ages, but with a significantly lower prevalence in animals less than 6 months old.     

Seroprevalence and risk factors of caprine toxoplasmosis in Minas Gerais, Brazil

The objective of this work was to carry out a study on caprine toxoplasmosis in the state of Minas Gerais, Brazil. To determine the prevalence of toxoplasmosis in goats in Minas Gerais, 767 sera from goats were tested by ELISA (enzyme-linked immunosorbent assay) and IFAT (indirect fluorescence antibody test). The prevalence of antibodies to Toxoplasma gondii was 43.0% and 46.0% by ELISA and IFAT, respectively. It was observed that 26.8% of the goats show low-avidity IgG to T. gondii. These results suggest the presence of animals in recent phase of toxoplasmosis in Minas Gerais. The risk factors for toxoplasmosis in goats were: age over 36 months (OR = 1.21; IC 95% 1.02–1.44), use of pen (OR = 1.83; IC 95%1.01–3.31) and pure breed animals (OR = 2.49; IC 95% 1.11–5.59).     

Occurrence of coligranulomatosis in coturnix quail in Uberlandia, Minas Gerais, Brazil

The occurrence of coligranulomatosis in a Brazilian flock of 1500 8-to-12-month-old coturnix quail is described. The disease caused an 85% drop in egg production and 15% mortality. Lesions were located on the mesentery, intestines, gizzard, heart, oviducts, ovaries, and liver. Samples of these organs were submitted for bacteriological culture, isolation, identification, pathogenicity assay by inoculation of diluted cultures into healthy hens, and histopathology.     

Heavy metals in horse blood, serum, and feed in Minas Gerais, Brazil

Pollution is a subject of worldwide concern and discussion and various areas of science are seeking to integrate their knowledge in an attempt to improve understanding of the harmful effects of modern human activities. Thus, the objective of the current study was to assess the potential for using the horse as a bio-indicator of environmental pollution. Blood and serum samples from 120 horses from locations with different degrees of urbanization and industrialization and the feeds used for these animals were analyzed to determine their heavy metal (Cd, Pb, Ni, Cu, and Zn) content. The data obtained were compared. The results did not show increases in heavy metal concentration in the blood and serum of the horses with the intensification of urbanization and industrialization around the farms. Only Cd, as determined in the blood of the animals, showed a certain potential for using horses as bio-indicators of environmental pollution. The data for sex, age, and chemical composition of the foodstuffs supplied to the animals were not determinants in explaining the variation in the concentrations of heavy metals observed.     

Populational dynamics of Stomoxys calcitrans (Linneaus) (Diptera: Muscidae) in three biocenosis, Minas Gerais, Brazil

Populational flux of the adult phase of Stomoxys calcitrans was observed in the municipal district of Pedro Leopoldo, Minas Gerais, Brazil. Three biocenoses were selected for the study: stable agrobiocenosis, pastural agrobiocenosis and eubiocenosis. The occurrence and the populational flux of the insects, using the Magoon trap for their capture, were established. For each trap located in different biocenoses, a crossbred calf (Bos taurus × Bos indicus) approximately 6-month-old was used as “live bait,” exposed weekly for 48 h in the traps. Of the three agrobiocenoses studied, the stable agrobiocenosis contributed the greatest number of specimens of. S. calcitrans captured, corresponding to 96.9% of the total flies of this species collected. S. calcitrans shows seasonal behavior for approximately 6 months (spring and summer being the rainiest months of the year). The population peaked during the months of November and December. During the months of July and August, there was no capture of flies.     

Strategic Control of Gastrointestinal Nematodes in Dairy Calves in Florestal,Minas Gerais,Brazil

Following epidemiological studies of gastrointestinal helminthiasis in dairy cattle in Florestal County, Minas Gerais, 80 Swiss and crossbred Zebu×Holstein calves, 8–10-months old, were selected to test the efficacy of three treatment protocols using ivermectin for helminth control. The calves were treated in Brachiaria grass paddocks, naturally infected with Haemonchus, Cooperia, Oesophagostomum and Trichostrongylus species, and then divided into four groups of 20 animals each: group 1 was treated with 200 g/kg body weight ivermectin in April (at the end of the rainy season) and October (beginning of the rainy season); group 2 was treated in April, August (middle of the dry season) and October; group 3 was treated in April, August, October and December (middle of the rainy season); and group 4 was left untreated as a control. The treatments effectively eliminated the worm burden only in groups 2 and 3 (p<0.05), although the calves continued to excrete Cooperia eggs after each treatment with ivermectin.     

Genetic diversity and molecular phylogeny of Anaplasma marginale isolates from Minas Gerais, Brazil

Anaplasma marginale (Rickettsiales: Anaplasmataceae), a tick-borne pathogen of cattle, is endemic in tropical and subtropical regions of the world, and many isolates of A. marginale may occur in a given geographic area. Phylogenetic relationships have been reported for A. marginale isolates from the US using gene and protein sequences of MSP1a and msp4. These studies demonstrated that msp4 sequences, but not MSP1a DNA or protein sequences, provide phylogeographic information and also that MSP1a sequences are highly heterogeneous among A. marginale populations. However, little information is available on the genetic diversity of A. marginale isolates from other regions of the world. The present study was undertaken to examine genetic variation among 10 isolates of A. marginale obtained from infected cattle in the State of Minas Gerais, Brazil, where A. marginale is endemic. Neighbor-joining analysis of msp4 sequences of Brazilian and New World isolates of A. marginale from Argentina, Mexico and the US provided bootstrap support for a Latin American clade. The sequences of the MSP1a repeats of four Brazilian isolates of A. marginale were compared to sequences of Latin American and US isolates. The MSP1a repeated sequences of Latin American isolates of A. marginale had nine repeat forms, alpha-phi, which have not been reported previously in North American isolates of A. marginale. Furthermore, the repeated forms tau, sigma and mu were only present in the Brazilian isolates. The results demonstrated that the genetic heterogeneity observed among isolates of A. marginale is common in endemic areas, independent of the predominant tick vector and is consistent with previous studies in which msp4 provided phylogeographic information about A. marginale isolates, while MSP1a was found not to be a useful marker for phylogeographic characterization of A. marginale isolates.     

Eco-epidemiology of visceral leishmaniasis in the urban area of Paracatu, state of Minas Gerais, Brazil

The present study was developed in the urban area of Paracatu, an endemic city for the American visceral leishmaniasis in Brazil. A six-month canine survey was performed with 6295 domiciled dogs in 28 districts in that area and showed that 4.2% of those (267 dogs) were positive for VL by ELISA and IFAT serum assays. Prevalence ratios for canine VL varied between 1.2% and 16.1%, depending on the district under investigation. Fifteen dogs - 80% of which were clinically asymptomatic for VL - were submitted to a more detailed study that comprised direct parasitological examination and Leishmania kDNA amplification of tissue samples as well as two PCR-RFLP methods using myelocultures. Leishmania amastigotes or Leishmania DNA were detected in all dogs but one. The infecting species of Leishmania was identified in about 50% (7/15) of the sample dogs: Leishmania (Leishmania) chagasi in two of them and, unexpectedly, Leishmania (Leishmania) amazonensis in the remaining five. Three months after the end of confiscation and elimination of the VL-seropositive dogs in the 28 districts of Paracatu, a systematic entomological survey was performed in five of them. Six hundred and sixty five (665) phlebotomine sand flies were captured in total, from which 89.5% were identified as Lutzomyia longipalpis. The population density of that species increased during the rainy season. Other thirteen (13) species of phlebotomine sand flies were captured at varying percentages from 0.2 to 5.0%. It is worth noting that L. longipalpis females were predominantely intradomicile when compared to males, suggesting that the VL transmission cycle in Paracatu may be occurring inside home.     

Occurrence of Trypanosoma evansi in Horses in the State of Minas Gerais,Brazil

Ttrypanosomosis caused by Trypanosoma evansi is a condition that causes significant losses to farmers in endemic areas. This study aimed to report one case of trypanosomiasis in the municipality of Itabira, state of Minas Gerais, Brazil. In November 2010, on a farm with 16 horses, three horses had clinical signs of anemia, limb edema, weight loss, lameness, muscle atrophy, and incoordination of the hind limbs. Trypanosomosis was suspected, and the animals with clinical signs were treated with two doses of diminazene aceturate (7 mg/kg, intramuscular) every 7 days; the treated animals recovered from the clinical symptoms. Blood samples were collected from six horses on the farm, including the three treated animals, to perform polymerase chain reaction specific for T evansi. Four samples were polymerase chain reaction negative, including those collected from three treated horses. However, two other asymptomatic horses were positive for the parasite based on the molecular testing. Based on the results, we concluded that the initial clinical suspect of trypanosomosis was correct, and the treatment used was effective. Probably the disease was introduced to Minas Gerais State through a stallion, which acquired the infection in an endemic area in southern Brazil.     

Seasonal Variation of Boophilus microplus (Canestrini, 1887) (Acari: Ixodidae) in Cattle in Minas Gerais State,Brazil

The seasonal variation of the tick Boophilus microplus in the `Regiaõ Metalúrgica' region of Minas Gerais state was studied using 26 Bos taurus (Holstein)×Bos indicus (Gir) calves, of which 16 animals were 3/4 Holstein×1/4 Gir and 10 were 3/4 Gir×1/4 Holstein. Monthly tick counts were made between March 1996 and March 1998 and, although B. microplus infestations occurred throughout the year, they were greater during the rainy season. Rainfall was the climatic factor that most affected the seasonal variation. The animals with a preponderance of Holstein blood presented infestations that were significantly (p<0.05) greater than those of the other cross. Five of the animals (19.2%) maintained 45.5% of the parasite load of the entire group.     

Epidemiological aspects of canine babesiosis in the semiarid area of the state of Minas Gerais, Brazil

Epidemiological aspects of Babesia vogeli infection were studied in the canine population of a rural town located in the Brazilian “Drought Polygon” of the state of Minas Gerais, Brazil. The survey was carried out in March 2003, when 505 dogs were identified and their characteristics registered on appropriate forms. Blood samples were collected at this time and again in June, September and December 2003. Serum samples were tested by the indirect fluorescent antibody test (IFAT) to detect antibodies against B. vogeli. The prevalence of anti-B. vogeli antibodies was 18.8%; however, no correlations were found between prevalence of infection and the age or gender of the animals. Cross-bred dogs presented a higher chance of acquiring infection in comparison to pure-bred dogs. Significant differences concerning the incidence of the disease were found during the period April–June in comparison to other months, demonstrating that transmission of B. vogeli is related to seasonal variations of tick infestations. The results indicate that climatic factors within the semiarid area interfere directly in the epidemiology of canine babesiosis.     

Importance of Lutzomyia longipalpis in the dynamics of transmission of canine visceral leishmaniasis in the endemic area of Porteirinha Municipality, Minas Gerais, Brazil

A study of Lutzomyia longipalpis (Lutz and Neiva, 1912) (Diptera: Psychodidae), the primary vector of American visceral leishmaniasis (AVL), and the canine form of the disease, was carried out in Porteirinha. The city is situated in the northern part of the Brazilian State of Minas Gerais and is an endemic area of AVL. Systematic phlebotomine captures were performed in seven districts with previously reported cases of canine visceral leishmaniasis, during 2 years (January 2000--December 2001). A total of 2328 specimens of L. longipalpis were captured. The association between the local climate variables and the population density of L. longipalpis was evaluated and rainfall was determined to be a major factor, with increased populations during the rainy season (October--March). At the same time period, blood samples from every dog domiciled in the same seven districts, in total 14,077 animals, were analyzed for infection by viscerotropic Leishmania using indirect immunofluorescence assay (IFA). Accumulated incidence rates of canine VL per district varied from 3.40 to 14.34 for the 2-year period. A positive correlation between the population density of L. longipalpis and the canine cases of visceral leishmaniasis in Porteirinha was observed.     

Distribution of equine infectious anemia in horses in the north of Minas Gerais State, Brazil.

The paper examines the prevalence of equine infectious anemia (EIA) in horse populations in the northern part (comprising 89 cities) of Minas Gerais State, Brazil, from January 2002 to December 2004. Data on 8,981 agar gel immunodiffusion test results from the region were used as input for a statistical and autoregressive analysis model to construct a city-level map of the distribution of EIA prevalence. The following EIA prevalence (P) levels were found: 49 cities with 0 < P < or = 0.5%, 26 with 0.5% < P < or = 1.5%, 10 with 1.5% < P < or = 5%, and 4 with 5% < P < or = 25%.     

Seroprevalence and risk factors for Neospora caninum in sheep in the state Minas Gerais, southeastern Brazil

The aim of this study was to determine the prevalence and risk factors associated with infection due to Neospora caninum in serum samples from 488 sheep originating from 63 farms in 63 municipalities distributed across eight of the twelve mesoregions of the state Minas Gerais, southeastern Brazil. For detection of N. caninum the sheep serum samples were subjected to the indirect fluorescence antibody test (IFAT ≥ 50). To identify the risk factors associated with infection due to N. caninum a questionnaire was filled out for each herd by interviewing, the individual responsible for the herd, demanding information on the general characteristics of the property. Sixty-four sheep sera (13.1%; 95% CI=10.3-16.4) presented IgG-specific anti-N. caninum antibodies with the following titers: 50 (49; 76.6%), 100 (7; 10.9%), 200 (4; 6.2%), 400 (3; 4.7%) and 800 (1; 1.6%). The prevalence of infected sheep per mesoregion ranged from 0 to 28.1%. Out of the 63 farms sampled, 31 (49.2%; 95% CI=36.4-62.1) presented at least one seropositive sheep. No significant association was found between the presence of anti-N. caninum antibodies and the risk factors evaluated on the farms, except for the mesoregion variable (p=0.004; OR=0.429; CI95%=0.182-1.008). These results indicate that there is a need for additional research to define the epidemiological importance of this parasite as a cause of reproductive problems in sheep herds in Minas Gerais.