On-line version ISSN 1678-4456
Braz. J. Vet. Res. Anim. Sci. vol.37 n.2 São Paulo 2000
Infecções naturais com nematódeos Filarioidea em Hydrochaerus hydrochaeris no Pantanal do Mato Grosso do Sul, Brasil
Adjair Antonio do Nascimento
Departamento de Medicina Veterinária Preventiva e Reprodução Animal
Faculdade de Ciências Agrárias e Veterinárias da UNESP
Campus de Jaboticabal
Via de Acesso Prof. Paulo Donato Castellane, s/n
14884-900 Jaboticabal SP
From 36 capybaras, slaughtered between 1989 and 1996, 11 young, less than 6 months old, and 25 adults, in the floodplain region of Mato Grosso do Sul, 570 Filarioidea nematodes were collected. Three hundred and ninety-four specimen of Cruorifilaria tuberocauda were collected from the renal arteries (380) and from pulmonary arteries (14) and 176 specimen of Yatesia hydrochoerus from the fasciae of skeleptical muscles, mainly from the obliquus externus abdominis region and from the internal faces of hind limbs.
UNITERMS: Nematoda; Filarioidea; Capybara; Hydrochaerus hydrochaeris.
The capybara (Hydrochoerus hydrochaeris, L. 1766), a wild rodent of semi aquatic habits, inhabits the surroundings of river banks, dams, bays and swamps. This rodent is, under domestication in several States of Brazil, with the aim of producing a high quality feedingstuff, of sound proteic value and low caloric content. It can be parasited by helminths which determine from gastrointestinal mucosa erosions to extense ceccum and colon ulcerations, endoarteritis, hypertrophia of vessel walls (intima and media) and renal pyramidal infarction.
The filariases of capybaras have been recently described in Venezuela2,4,10,11, Colombia5,12,13 and Brazil1,3,8,9. In these studies, five species of Filarioidea were identified: Dirofilaria acutiuscula, Cruorifilaria tuberocauda, Yatesia hydrochoerus, Mansonella longicapita and Mansonella rotundicapita. The objectives of the present study were to determine the species of Filarioidea which parasite capybaras in the floodplain of Mato Grosso do Sul, as well as to investigate the characteristics of infections, such as: prevalence, intensity, mean intensity and abundance.
MATERIAL AND METHOD
The floodplain region of Mato Grosso do Sul (Paiaguás) is an ecological system with an area of 25,457 km2, of open pasture with patches of stunted vegetation, well-defined wet and dry seasons and a mean temperature about 28ºC in summer
Thirty-six capybaras, 11 young (less than 6 months old) and 25 adults, infected naturally, slaughtered in the floodplain between 1989 and 1996, in the counties of Pedro Gomes (7), Corumbá (17) and Coxim (12), Mato Grosso do Sul, were used in this study.
Following the slaughter, each animal was esfoliated, and skin and carcass examined macroscopically (muscle fasciae). Approximately 50% of the skin was divided into fragments of 30 cm2 and maintained for 3 hours in water-bath, in metal trays containing a thin layer (2 cm) of saline solution (0.85% of NaCl) at the temperature of 37ºC. At the end of this period, the obtained material was macroscopically examined and the worms found, both in the muscle fasciae and the skin, were fixed in formol-acetic. Immediately after the host death, the examination of the heart blood vessels, lungs and kidneys was conducted by incision with a 10.5 cm thin end pair of scissors. The morphological studies of nematodes were accomplished5,13, after the consecutive diafanization in glacial acetic acid and Faya creosoto. Renal fragments were fixed in Bouin fluid, processed routinely, and stained with hematoxiline-eosin. The ecological terms (prevalence, intensity, mean intensity, abundance) are the committees recommendations of the American Society of Parasitologists6.
In 13 capybaras Filarioidea nematodes were not found; 11 of these capybaras were young animals aging less than 6 months old. Infections with only one species of worm were observed in ten animals, and in 13 with 2 nematodes species. The total worm burden found in 23 capybaras was 570 nematodes adults, being 176 specimens of Y. hydrochoerus obtained from the fasciae, obliquus externus abdominis, region mainly in the internal face of the muscles from the hind limbs, and occasionally from the lumbar region (Fig. 1A) and 394 specimen of C. tuberocauda from the renal (380 worms) (Fig. 1B) and pulmonary arteries (14 worms) (Tab. 1).
Prevalence, intensity, mean intensity and abundance of the Filarioidea nematodes parasites of the renal and pulmonary arteries and fasciae of skeleptical muscles, found in capybaras slaughtered between 1986 and 1996 in the counties of Pedro Gomes, Corumbá and Coxim, from floodplain region of Mato Grosso do Sul, Brazil.
The number of Y. hydrochoerus varied from 1 to 40 worms per animal and C. tuberocauda counts ranged from 1 to 134 nematodes.
In relation to the pathogeny of C. tuberocauda, which develops mainly in the capybara kidneys, the hystopathological examination showed that the main lesions occurred in the artery walls and consisted of endoarterites, hypertrophia of the vessel walls (intima and media) and rugged protuberance which invades the arterial lumen, causing renal pyramidal infarction. Renal arteries hasting dead and decalcified worms, granulomatous proliferation reached to the renal parenquima (Fig. 1C). Besides these lesions, a renal atrophy and presence of marked depressions on the surface of the organ were observed (Fig. 1D), suggesting cicatricial lesions.
Marked depression on the surface of kidney parasited by C. tuberocauda HE (obj X).
The careful examination of skeleptical muscle fasciae taken immediately after slaughtering the animals, revealed the presence of Y. hydrochoerus in 47% of the capybaras. The adult worms do not produce important lesions (Fig. 1A), but their presence in the fasciae represent objections to the commercialization of frozen meat. The results of the infection intensity of Y. hydrochoerus, characterized by low and moderate values (Tab. 1), differed from the high rates of prevalence (93.5%) observed in Colombia13, but on the other hand were similar to the data obtained in Brazil3,9.
The observations on the basic characteristics of infections of C. tuberocauda revealed a prevalence of 52.7%, which are similar to data presented by other authors2,3,8,9,10 and differed from those reported in Colombia5. Besides, low values of mean intensity (20.7 worms) and of abundance (10.94 nematodes) were obtained in this study.
The renal lesions observed in the present study were similar to those in Colombian capybaras7 that presented villous endarteritis, intimal and medial hypertrophy of the vessel walls and large rugose protuberances that encroached upon the lumen leading to pyramidal infarcts in the kidneys. The renal atrophy and depressions found on the surface of the organ (Fig. 1D) seem to be related to the areas of tecidual retraction, due to the proliferation of the intertubular conective tissue.
Foram coletados 570 nematódeos Filaroidea de 36 capivaras, sacrificadas entre 1989 e 1996, onze jovens menores que seis meses e 25 adultas, provenientes da região do pantanal do Mato Grosso do Sul (Paiaguás). Cento e setenta e seis (176) espécimes de Yatesia hydrochoerus foram encontrados nas fáscias dos músculos esqueléticos, principalmente da região do obliquus externus abdominis e na face interna dos membros posteriores e trezentos e noventa e quatro (394) espécimes de Cruorifilaria tuberocauda foram coletados das artérias renais (380) e das artérias pulmonares (14) dos animais.
UNITERMOS: Nematoda; Filarioidea; Capivaras; Hydrochaerus hydrochaeris.
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1 Departamento de Medicina Veterinária Preventiva e Reprodução Animal da Faculdade de Ciências Agrárias e Veterinárias da UNESP, Campus de Jaboticabal SP