Relationship Between Blood-borne Parameters and Gross Lesions in Leishmania chagasi Seroreagents Dogs

Canine visceral leishmaniasis, a systemic and chronic zoonosis, is caused in Brazil by the protozoan Leishmania chagasi, a widely accepted synonym for Leishmania infantum. The agent and disease has recently arrived in Uberlândia city, Minas Gerais, Brazil. In this research, hematological parameters and gross lesions of dogs with visceral leishmaniasis were compared, to highlight aspects of disease in a recent outbreak. For this purpose forty mongrel dogs from Uberlândia seroreagents by ELISA and RIFI tests were selected. Animals were categorized as asymptomatic,(AS); oligosympytomatic (OS) and symptomatic (SS). Blood samples were collected and dogs were euthanized according to Brazilian Federal rules. Animals were then submitted to standard necropsy procedures at Veterinary Pathology sector of the Federal University of Uberlândia. Most prominent alterations were of observed in respiratory and integumentary systems, with pilose rarefaction (OS: 41.7%, SS: 60.1%), specially periocular (OS: 25.0 %, SS: 26.1%) and thoracic/pelvic members (OS: 25.0%, SS: 30.4%). Onychogryphosis (OS: 41.7%, SS: 39.1%), pulmonar edema (OS: 25.0%, SS: 39.1%), and congestion (OS: 41.7%, SS: 60.9%). Moreover animals displayed increase of several organs; liver (67.5%), spleen (60%), lymph nodes (72.5%) and kidney (47.5%). Hematological alterations included low red cell counts and decreased hemoglobin content. Overall, 27.5% of animals presented leukocitosis, 52.5 % of dogs had increased band neutrophil counts 5.0 % had basophilia and 42.5% monocytopenia. No correlations was found between hematological findings and clinical status of animals (asymptomatic, oligosymptomatic or symptomatic). Presumptively, we can conclude that, in asymptomatic animals there are hematological as well as gross alterations.(AU)

Antigens from Rhipicephalus sanguineus ticks elicit potent cell-mediated immune responses in resistant but not in susceptible animals.

In the present study we compared the immunological reactions between Rhipicephalus sanguineus tick-infested susceptible (dogs and mice) and tick-resistant hosts (guinea pigs), elucidating some of the components of efficient protective responses against ticks. We found that T-cells from guinea pigs infested with adult ticks proliferate vigorously in the presence of concanavalin A (ConA), whereas ConA-induced cell proliferation of tick-infested mice and dogs was significantly decreased at 43.1 and 94.0%, respectively, compared to non-infested controls. Moreover, cells from mice and dogs submitted to one or three successive infestations did not exhibit a T-cell proliferative response to tick antigens, whilst cells from thrice tick-infested guinea pigs, when cultured with either a tick extract or tick saliva, displayed a significant increase in cell proliferation. Also, we evaluated the response of tick-infested mice to a cutaneous hypersensitivity test induced by a tick extract. Tick-infested mice developed a significant immediate reaction, whereby a 29.9% increase in the footpad thickness was observed. No delayed-type hypersensitivity (DTH) reaction was detected. Finally, the differential cell count at the tick attachment site in repeatedly infested mice exhibited a 6.6- and 4.1-fold increase in the percentage of eosinophils and neutrophils, respectively, compared to non-infested animals, while a decrease of 77.0-40.9 in the percentage of mononuclear cells was observed. The results of the cutaneous hypersensitivity test and the cellular counts at the tick feeding site for mice support the view that tick-infested mice develop an immune response to R. sanguineus ticks very similar to dogs, the natural host of this species of tick, but very different from guinea pigs (resistant host), which develop a DTH reaction in addition to a basophil and mononuclear cell infiltration at the tick-attachment site. In conclusion, saliva introduced during tick infestations reduces the ability of a susceptible animal host to respond to tick antigens that could stimulate a protective immune response. As a consequence, the animals present a lack of DTH response and disturbed cellular migration to tick feeding site, which can represent a deficient response against ticks.

Life cycle and host specificity of Amblyomma triste (Acari: Ixodidae) under laboratory conditions.

We report biological data of two generations of Amblyomma triste in laboratory and compared the suitability of different host species. Infestations by larval and nymphal stages were performed on guinea pigs (Cavia porcellus), chickens (Gallus gallus), rats (Rattus norvegicus), rabbits (Oryctolagus cuniculus), wild mice (Calomys callosus), dogs (Canis familiaris) and capybaras (Hydrochaeris hydrochaeris). Infestations by adult ticks were performed on dogs, capybaras and rabbits. Tick developmental periods were observed in an incubator at 27 degrees C and RH 90%. Guinea pigs were the most suitable hosts for larvae and nymphs, followed by chickens. The remaining host species were less suitable for immature ticks as fewer engorged ticks were recovered from them. Mean larval feeding periods varied from 3.8 to 4.7 d between different host species. Mean larval premolt periods ranged from 8.9 to 10.4 d. Nymphal mean feeding periods varied from 4.2 to 6.2 d for ticks fed on different host species. Premolt period of male nymphs (mean: 15.4 d) was significantly longer than that of female nymphs (14.7 d). Female nymphs were significantly heavier than male nymphs. The overall sex ratio of the adult ticks emerged from nymphs was 0.9:1 (M:F). Capybaras were the most suitable host for the tick adult stage as significantly more engorged females were recovered from them and these females were significantly heavier than those recovered from dogs or rabbits. The life cycle of A. triste in laboratory could be completed in an average period of 155 d. The potential role of guinea pigs, birds and capybaras, as hosts for A. triste in nature, is discussed.