FASES DE LARVA Y NINFA DE Amblyomma cajennense (ACARI: IXODIDAE) EN RATAS (Rattus norvegicus) ESPLENECTOMIZADAS E INTACTAS: ESTUDIO DE CASOS Larval and Nymphal Stages of Amblyomma cajennense (Acari: Ixodidae) in Esplenectomized and Intact Rats (Rattus norvegicus): Case Studies

This work has to main objectives: 1) to carry out the larvae and nymphal stages of Amblyomma cajennense in Sprague Dawley rats (Rattus norvegicus), a rodent considered resistant to this ectoparasite, and 2) to assess the role of the rat’s spleen as a lymphoid organ which may control the development of the tick population. Rats were divided into three groups: 1) Experimental Group (EG) with splenectomized (ENTZ) rodents, 2) Control Group (CG), with spleen or intact rats, and 3) Super Control Group (SCG) with intact and A. cajennense unifected rodents. Rats of the EG and CG group were infected with a dosis of around 300 starving larvae, which after 3 to 6 days completed the process of haematophagia. The total amount of engorged larvae and of collected nymphae was 3.5 times greater in the EG than in the CG group. The histopathologic diagnosis of spleen samples from A. cajennense infected rats (CG) showed a greater amount of large lymphoid follicles with hyperplasia of lymphocytes, plasmocytes, and macrophages, which means activated splenic focuses, a similar tissue reaction was not observed in spleen samples of A. cajennense uninfected rats. This histopathologic diagnosis found in the spleen of infected rats (CG) seems to point that the spleen has an active role in the control of A. cajennense evolutive stages, at least in Sprague Dawley rats. The haematologic study performed to rats at all groups showed a marked thrombocytopenia in all A. cajennense infected rats, which appears to be caused by pharmacological factors inoculated into the host with the saliva during the bloodsucking process. Not only the splenic tissue would have a role in the rat’s resistance to A. cajennense infections, but it may participate other immunological, histological, and physiological factors.

[1]  R. Rico-Hesse,et al.  Mosquito Bite Delivery of Dengue Virus Enhances Immunogenicity and Pathogenesis in Humanized Mice , 2012, Journal of Virology.

[2]  A. Mancebo,et al.  Valores hematológicos y bioquímicos de las ratas Sprague Dawley producidas en CENPALAB, Cenp: SPRD , 2011 .

[3]  J. Haddad,et al.  Biological parameters of ticks (Amblyomma cajennense Fabricius, 1787) under field and laboratory conditions in Pedro Leopoldo, State of Minas Gerais, Brazil. , 2008, Revista brasileira de parasitologia veterinaria = Brazilian journal of veterinary parasitology : Orgao Oficial do Colegio Brasileiro de Parasitologia Veterinaria.

[4]  F. Gallagher.  Streptococcus infection and splenectomy , 2001, The Lancet.

[5]  D. Waghorn,et al.  Overwhelming infection in asplenic patients: current best practice preventive measures are not being followed , 2001, Journal of clinical pathology.

[6]  R. C. Leite,et al.  Host specificity of Amblyomma cajennense (Fabricius, 1787) (Acari: Ixodidae) with comments on the drop-off rhythm. , 1998, Memorias do Instituto Oswaldo Cruz.

[7]  J. Sauer,et al.  Tick saliva: recent advances and implications for vector competence , 1997, Medical and veterinary entomology.

[8]  J. Ribeiro.  Role of saliva in tick/host interactions , 1989, Experimental & Applied Acarology.

[9]  N. Barré,et al.  Heartwater in the Caribbean , 1984 .

[10]  M. D. Silvio,et al.  Efectos de las citocinas esplénicas sobre la función hepatocelular: la esplenectomía disminuye la producción hepática de óxido nítrico , 2003 .

[11]  Antonio Pardo Merino,et al.  SPSS 11: Guía para el análisis de datos , 2002 .