EVIDENCE OF SPOTTED FEVER GROUP RICKETTSIAE IN STATE OF RIO DE JANEIRO, BRAZIL
Tatiana ROZENTAL (1), Maria Cristina BUSTAMANTE(2), Marinete AMORIM(3), Nicolau Maués SERRA-FREIRE(3) & Elba Regina Sampaio de LEMOS(1)
Ticks were obtained from dogs from February to September of 1999 at weekly intervals, in the County of Piraí, State of Rio de Janeiro. Four hundred seventy four ixodids were taxonomically identified, 103 Amblyomma cajennense, seven Amblyomma ovale, 209 Rhipicephalus sanguineus, and 155 Amblyomma sp. An hemolymph test associated with Giemsa’s stain revealed two specimens in 163 ticks tested (R. sanguineus and Amblyomma sp), containing rickettsia-like organisms. Direct immunofluorescence verified the presence of spotted fever group rickettsia in one specimen of R. sanguineus. Considering the limited information on rickettsiosis in Brazil, principally in relation to the vectors involved in perpetuating it in foci, these preliminary results give us an idea on the importance of infection in ticks, allowing to expand our knowledge on this zoonosis.
KEYWORDS: Spotted fever; Ticks; Hemolymph test; Brazil
Brazilian spotted fever (BSF), caused by Rickettsia rickettsii, is the most significant tick-borne disease in Brazil33,46.
five districts: Piraí, Monumento, Arrozal, Pinheiral, and Santanésia12,16. Ticks were collected in two neighborhoods, Cacaria and Serra do Matoso, in the District of Monumento (Fig. 1).
The Cayenne tick9,17,47 (Amblyomma cajennense) is the most important vector of R. rickettsii, and humans are frequently bitten by larvae and nymphs of this arthropod.
Other groups of ixodids have also been implicated as transmissors and/ or reservoir of this zoonosis such as Amblyomma ovale, Amblyomma braziliensis, Amblyomma cooperi, Rhipicephalus sanguineus14,23,29,30,31,32,36,45.
With the help of a veterinarian and two employees of the county’s health office, 578 ticks were captured between February and September 1999. The arthropods were collected weekly from dogs and taxonomically identified1,2,39 at the Department of Entomology, Laboratory of Ixodids, Oswaldo Cruz Institute. After entomologic analysis, the ticks were submitted to investigation for rickettsiae.
Although most cases occurred in the Brazilian Southest region, these
The ticks were desinfected with 10% formaldehyde solution, 70% alcohol and washed in sterile distilled water for five minutes.
ticks are distributed throughout Brazil15,19,20,21,28,40,41,42,43
. The absence of
officialy reported cases of BSF in other regions may be due in part to the lack of confirmatory diagnostic tests and clinical suspicion.
This paper provides preliminary results on rickettsia-infected ticks in an area within the State of Rio de Janeiro, where sporadic cases of BSF has been confirmed since 1970’.
For each live tick, two slides were prepared with the hemolymph, fixed in alcohol and acetone for 15 minutes5. The first slide was used for investigation of rickettsia-like organisms using Giemsa staining, and the second for the direct immunofluorescence test with R. rickettsii positive human serum and fluorescein.
MATERIALS AND METHODS
The County of Piraí was chosen for this study based on three cases of BSF (two in 1977 and one in 1997) which have been confirmed in a neighbouring county, Barra do Piraí, and for the support offered by the County´s Health Department to collaborate.
The County of Piraí is located in the Medio Paraíba Industrial Region in the State of Rio de Janeiro (22°37’44”S, 43°53’59”W) that consists of
Of the 578 ixodids collected from 129 dogs, 474 ticks were taxonomically identified (Table 1): 103 A. cajennense, seven A. ovale, 209 R. sanguineus, and 155 Amblyomma sp. (Table 2).
Hemolymph test and Giemsa staining: Of the 163 ticks submitted to hemolymph test, Giemsa staining was performed in only 153 ixodids (32.2%), due to loss of material (slides). One nimph Amblyomma sp. displayed intracellular rickettsia-like particles in the nucleus and the
Department of Virology, Institute Oswaldo Cruz, FIOCRUZ, Rio de Janeiro, RJ, Brasil.
Division of Health of Municipality of Piraí, Piraí, Rio de Janeiro, Brasil.
Department of Entomology, Institute Oswaldo Cruz, FIOCRUZ, Rio de Janeiro, RJ, Brasil.
Correspondence to: Tatiana Rozental. Department of Virology, Institute Oswaldo Cruz, FIOCRUZ Av. Brasil 4365, 21045-900 Rio de Janeiro, RJ, Brasil. Phone: + 55-21-2598-4274; Fax: + 55-21-2270-6397; E-mail: email@example.com