Acquired resistance of horses to Amblyomma cajennense (Fabricius, 1787) ticks

Acquired immunity of horses to larvae, nymphs and adults of the Amblyomma cajennense tick was evaluated through three consecutive experimental infestations of tick-bite naive hosts. Data from these infestations were compared to those from field-sensitized horses and donkeys. It was observed that tick-bite naive horses developed a low level of resistance after two infestations as shown by a significant decrease in larval yield and a tendency for lower engorged weight of nymphs during third infestation. Ticks fed on field-sensitized horses had a similar biological performance to that observed on the third infestation of tick-bite naive horses but the mean engorged nymph weight was significantly lower than that of the first infestation from tick-bite naive horses. Donkeys presented the strongest resistance with significantly lower engorged weights of all instars and of the egg mass compared to the first infestation of tick-bite naive horses. Donkeys also displayed a significantly higher resistance than field-sensitized horses as demonstrated by significantly lower egg mass weights. Overall these results indicate that donkeys but not horses maintain a strong resistance to A. cajennense ticks. The importance of these findings in relation to vectoring of tick-borne diseases is discussed. (C) 2003 Elsevier B.V. All rights reserved.

Biological and DNA evidence of two dissimilar populations of the Rhipicephalus sanguineus tick group (Acari : Ixodidae) in South America

In this work, the biology, mitochondrial DNA and fertility of hybrids from two strains of Rhipicephalus sanguineus, from Brazil and Argentina, were compared. Engorged larvae, nymphs and adults from Argentina weighed more and the engorgement period of adult females was significantly longer than those of their Brazilian counterparts, whereas adult female tick yield rate was higher for the Brazilian strain. High intraspecific divergence of mitochondrial DNA was detected between R. sanguineus from Brazil and Argentina. on the other hand, a strong genetic relationship was detected between European and Argentinean R. sanguineus populations while the Brazilian population appeared to be related to the African Rhipicephalus turanicus. Adult hybrid females laid eggs, which were mostly unviable, whereas a mean of more than 1400 larvae hatched per egg mass from pure Brazilian and Argentinean strains. These results showed that differences between these strains are greater than previously assumed and that the biosysternatic status of R. sanguineus ticks from South America should be re-evaluated. Wide variations, such as these might account for the reported worldwide differences in biology and vector capacity of this species. (c) 2005 Elsevier B.V. All rights reserved.

Skin hypersensitivity tests in buffaloes parasitized with Toxocara vitulorum.

Skin tests were done using larval extract and excretory-secretory (ES) antigens injected intradermally in the neck area of 30, 11- to 200-day-old buffalo calves and nine 27- to 100-day postparturition buffalo cows, the skin of the buffaloes infected with Toxocara vitulorum, mainly calves, demonstrated a hypersensitive response to antigens, especially to the larval extract antigens. Skin hypersensitivity responses were characterized by the presence of dermal nodules with progressive induration and an increase of up to four times the size of the original area at 30 min (immediate type) and at 72 h (delayed type) after injection, Histological preparations of skin reactions at 72 h showed a typical mononuclear cell infiltration, with eosinophils and perivascular cuffing in most of the animals, Fecal examination of 75 animals showed that 65 (86.7%) buffalo calves (9-115 days old) were parasitized with T. vitulorum. The peak of egg output from these animals occurred when they were approximately 45 days old.

Evaluation of transformation growth factor beta(1), interleukin-10, and interferon-gamma in male symptomatic and asymptomatic dogs naturally infected by Leishmania (Leishmania) chagasi

The aims of this study were to evaluate the immunomodulatory role of TGF-beta(1), 1L-10, and INF-gamma in spleen and liver extracts and supernatant cultures of white spleen cells from male symptomatic and asymptomatic dogs, naturally infected by Leishmania (Leishmania) chagasi. Thirty dogs from Aracatuba, São Paulo, Brazil, an endemic leishmaniosis area, were selected by positive ELISA serological reaction for Leishmania sp. and divided into two groups: asymptomatic (n=15) and symptomatic (n=15) consisting of animals with at least three characteristic signs (fever, dermatitis, lymphoadenopathy, onychogryphosis, weight loss, cachex a, locomotion problems, conjunctivitis, epistaxis, hepatosplenomegaly, edema, and apathy). After euthanasia, spleen and liver fragments were collected for ex vivo quantification of TGF-beta(1), IL-10, and INF-gamma. Naturally active in vitro produced TGF-beta(1) was also evaluated in spleen cell culture supernatant. Spleen and liver extract of asymptomatic dogs had higher mean TGF-beta(1) levels than symptomatic dogs. High concentrations of IL-10 were found in spleen, and mainly in liver extract of both groups. Higher INF-gamma concentrations were found in spleen extracts of symptomatic dogs, and in liver extracts of asymptomatic dogs. Extract of this cytokire was lower in spleen extract. Although INF-gamma is being produced in canine infection, mean levels of TGF-beta(1) and IL-10 from spleen and liver extracts were quantitatively much higher; suggesting that immune response in both asymptomatic and symptomatic dogs A as predominantly type Th2. (c) 2006 Elsevier B.V. All rights reserved.

Experimental toxoplasmosis in broiler chicks

To evaluate chicken toxoplasmosis both as an economic and a public health subject, 84 broiler chicks of a commercial strain, 30 days old, were distributed into seven groups of 12 birds (three replications of four chicks) experimentally infected with three developing T. gondii stages of the P strain as follows: tachyzoites. intravenous (two groups: 5.0 x 10(5) and 5.0 x 10(6)), cysts, per os (two groups: 1.0 x 10(2) and 1.0 x 10(3)) and oocysts, per os (three groups: 5.0 x 10(2), 5.0 x 10(3) and 5.0 x 10(4)). Twelve chicks received only a placebo (control group). During the next 30 days the following parameters were estimated: productivity (weight gain and feed conversion), clinical signs, including rectal temperature and parasitemia (bioassay). No clinical signs suggesting toxoplasmosis were seen and no statistical differences on productivity standards were found in comparison between inoculated and control chicks. However, fowls inoculated with tachyzoites and oocysts occasionally showed hyperthermia. Some haematological changes were detected in fowls inoculated with T. gondii. Anatomo-histopathological changes were not observed. From 14 parasitemias detected, 35.7% appeared on the 5th day after inoculation and 57.1% of them resulted from oocysts inoculation. After 30-35 days all birds were slaughtered: fragments from 12 organs or tissues from each of them were subjected to artificial peptic digestion and after that injected into T. gondii antibody-free mice (IIFR). T. gondii was detected in brain (12), pancreas (five), spleen (five), retina (five), kidney (two), heart (four), proventriculus (three), liver (two), intestine (two), lung (one), and skeletal muscle (one). Similar to observations with parasitemia, from 42 T. gondii isolations, 59.5% came from chicks which had received oocysts. It can thus be inferred that the developing form, expelled by cats, is the most important for T. gondii chicken infection and that brain is the most infected organ in birds. Attention must be paid to the potential importance of chicken meat in public health, since T. gondii was isolated from skeletal and heart muscles. (C) 1997 Elsevier B.V. B.V.

Species diversity and seasonality of free-living ticks (Acari : Ixodidae) in the natural habitat of wild Marsh deer (Blastocerus dichotomus) in Southeastern Brazil

This study evaluated the presence and seasonal activity of free-living ticks in remaining marsh areas by the Parana river, in Brazil. Eight field trips (once per season) for collection of ticks were performed during 2 years. Using CO2 traps, dragging, and visual inspection of vegetation, five free-living tick species were collected, in the following order of abundance: Amblyomma cajennense, Amblyom\ma dubitatum, Amblyomma triste, Amblyomma coelebs, and Amblyomma nodosum. The seasonal pattern of A. cajennense was characterized by the highest peaks for adult ticks in the summer/spring months, for nymphs in the winter and for larvae in the autumn and winter. A. dubitatum and A. triste presented similar seasonal patterns characterized by peaks of adult ticks in the autumn. Nymphs of A. dubitatum peaked in the winter of the first year and in the winter/spring of the second year. A. triste was the only species to be collected in significantly higher numbers in the marsh than in surrounding drier areas such as forest patches. Among domestic animals living close the marsh areas, horses were infested by Anocentor nitens, A. cajennense, and Boophilus microplus, bovines were infested solely by B. microplus, and dogs were infested by Rhipicephalus sanguineus. Adults of A. triste showed to be well adapted to the marsh environment. This result, at least partially, explains local previous observations on the association of A. triste with marsh deer, as this vertebrate host inhabits mainly the marsh area. (c) 2006 Published by Elsevier B.V.

Antibodies to Neospora caninum and Toxoplasma gondii in domestic cats from Brazil

The occurrence of antibodies to Neospora caninum and Toxoplasmagondii was determined in 400 domestic cats (Siamese, Persian, and undetermined breeds) from the Municipality of Aracatuba, São Paulo, Brazil, through the indirect fluorescence antibody test (IFAT). of the 400 cats, 100 were seropositive to T. gondii (25%, titer >= 64) and 98 to N. caninum (24.5%, titer >= 16). The rate of seropositive cats for T. gondii was correlated with age (chi(2)=35.7; p < 0.001), with a higher number of infected animals at older ages. of the 219 cats younger than 1-year-old, 13.2% were seropositive for T. gondii, while 39.2% were positive in the 181 older animals. The presence of N. caninum was also correlated with age (divided by(2)=8.8; p < 0.01), with 18.7% (41/219) and 31.5% (57/181) of positive animals at ages below and above 12-month, respectively. An association between the occurrences of both protozoa in the felines was also observed (chi(2)=19.6; p < 0.001).

Hepatozoon canis infection of wild carnivores in Brazil

Hepatozoon canis was diagnosed in a crab-eating fox (Cerdocyon thous) found on a highway in the region of Botucatu, São Paulo, Brazil, after being hit by a car. The fox had bilateral fractures of the olecranon, which was corrected by osteosynthesis. Hematologic findings included a neutrophilia, eosinophilia, monocytosis and mild anemia. In the Leishman-stained blood film, gametocytes of Hepatozoon canis in neutrophils were identified measuring 9.1+/-0.54x5.3+/-0.46 mu m. (C) 1997 Elsevier B.V. B.V.

Evaluation of serological tests for the diagnosis of Neospora caninum infection in dogs: Optimization of cut off titers and inhibition studies of cross-reactivity with Toxoplasma gondii

Diagnosis of Neospora caninum infection in dogs is based on serological assays such as the indirect fluorescent antibody test (IFAT) and enzyme-linked immunosorbent assays (ELISA). This study evaluated two serological tests (IFAT and ELISA) for the detection of IgG antibodies to N. caninum in 300 serum samples of dogs through the optimization of cut off titers by using the two-graph receiveroperating characteristic (TG-ROC) curve. In addition, the identification of major cross-reactive antigens with Toxoplasma gondii was investigated by inhibition ELISA and immunoblotting (IB) assays. IFAT and ELISA results showed 74% agreement, with a good negative concordance (P-neg=0.83), but a poor positive concordance (P-pos=0.42). The great majority (86%) of sera with positive concordant results (IFAT+/ELISA+) recognized at least two out of three N. caninum immunodominant antigens, particularly the 29-32 and 35-37 kDa bands. Optimization of cut off titers in IFAT and ELISA was performed considering the reactivity to at least two out of three N. caninum immunodominant antigens as infection markers, obtaining a titer of 50 for IFAT and 200 for ELISA. Seropositivity to N. caninuin was significantly associated with T gondii-seropositive samples, particularly in ELISA (55.4%). Inhibition ELISA curves for N. caninum showed a partial heterologous inhibition, indicating some degree of cross-reactivity between N. caninum and T gondii antigens. Inhibition IB assays showed a moderate heterologous inhibition for N. caninum antigens above 45-50 kDa. These results indicate that ELISA should be used critically when crude tachyzoite antigen preparations are employed, due to possible cross-reactivity with other related parasites as T gondii. Also, the cut off dilution of 1:50 in IFAT showed to be the most appropriated for N. caninum serology in dogs. Therefore, we suggest that N. caninum immunodominant antigens, specially the 17 and 29-32 kDa proteins, should be selected markers in serological assays for canine neosporosis. (c) 2006 Elsevier B.V. All rights reserved.

Seroepidemiology of Toxoplasma gondii, Neospora caninum, and Leishmania spp. infections and risk factors for cats from Brazil

The seroprevalence of infection by Toxoplasma gondii, Neospora caninum, and Leishmania spp. was detected through an indirect immunofluorescence in 70 cats from the Andradina Municipality, São Paulo State, Brazil. Anti-T. gondii antibodies (titer >64) were detected in 15.7% (11/70) of animals, whereas positivity for N. caninum (titer 16) was not observed in any animal. of the cats from urban and rural areas, 10.4% (5/48) and 27.2% (6/22) were positive for T. gondii, respectively. Breed, age, food, and contact with animals of other species were significant for considering the positivity for T. gondii (P <= 0.0001). Cats having access to streets (17.1%, 11/64), cats cohabiting with rats (19.6%, 10/51), and cats feeding on homemade food and raw milk (27.2%, 6/22) were positive for T. gondii. In addition, 4.2% (3/70) of the cats were positive for Leishmania spp. by ELISA technique and negative by IFAT without coinfection with T. gondii and Leishmania spp. There was no serological positivity against feline immunodeficiency virus or feline leukemia virus. In conclusion, T. gondii infection in part of the feline population from Andradina is not linked to immunosuppressions or coinfections but probably to postnatal infection in association with the type of diet and presence of rats.

Comparison of two immunochromatographic assays and the indirect immunofluorscence antibody test for diagnosis of Trypanosoma cruzi infection in dogs in south central Louisiana

Two rapid tests evaluated in dogs considered to be of high risk of Infection with the Chagas parasite Trypanosoma cruzi using two immunochromatographic assays. Trypanosoma Detect (TM) for canine, InBios, Seattle, WA and CHAGAS STAT-PAK (TM) assay, Chembio Diagnostic Systems, Medford, NY, in south central Louisiana. For this purpose a serological survey was carried out in a total of 122 dogs and a serum bank was created. These 122 animals were first tested by IFAT that was used as the standard test From the serum bank 50 samples were tested using the two rapid Chagas assays and results compared to the standard test IFAT The serological survey using IFAT showed it prevalence of T cruzi infection in 22.1% of the tested dogs. In the immunochromatographic assays. 13 and 11 animals were positive on rapid assay Trypanosoma Detect (TM) for canine, InBios and CHAGAS STAT-PAK (TM), Chembio Diagnostic Systems, respectively compared to 11 positive by IFAT. These two immunochromatographic tests have shown high susceptibility and specificity compared to our standard method IFAT. The rapid, easy and accurate screening assays used in conjunction with confirmatory tests, would be an excellent tool for veterinarians to diagnose T cruzi infection. Early detection of T cruzi infection may prevent complications through an effective treatment. Greater awareness by veterinarians of the risk. clinical findings, history along with diagnostic methods will contribute greatly to an understanding of the true prevalence of Chagas disease in dogs in Louisiana. (c) 2009 Elsevier B.V. All rights reserved.