Natalia Marina Cardillo

Trichinella infection in wild animals from endemic regions of Argentina

Natural infection with Trichinella has been described in more than 150 mammalian species. However, few reports of Trichinella infection in wild animals have come from Argentina. In this study, muscle tissue was obtained from wild animals in Argentina with the aim of evaluating the presence of Trichinella. A total of 169 muscle samples were collected to determine the presence of Trichinella larvae by artificial digestion. The 169 muscle samples originated from 12 species including 36 opossums (Didelphis albiventris), 19 armadillos (Chaetophractus villosus), 9 capybaras (Hydrocaeris hydrocaeris), 1 puma (Puma concolor), 3 grey fox (Lycalopex gymnocercus), 6 coypus (Myocastor coypus), 6 skunks (Conepatus chinga), 2 ferrets (Galictis cuja), 66 rats (Rattus norvegicus), 6 mice (Mus musculus), 12 wild boars (Sus scrofa), and 3 wild cats (Felis geoffroyi). Trichinella infection was detected in 1 puma [2 larvae per gram (LPG)], 3 wild boars (8–420 LPG), 3 armadillos (0.04–0.08 LPG), and 9 rats (0.1 to 150 LPG). Only 3 Trichinella isolates, of 1 rat and 2 wild boars from Neuquén, were identified as Trichinella spiralis by nested PCR. The presence of Trichinella infection among wild animal populations suggests a sylvatic cycle of transmission in Argentina, which can serve as a reservoir for humans and domestic animals. Further, evidence of high prevalence in rats emphasizes the need to improve pig management, mainly in small individual farms without adequate technology, to enhance the quality of feeds, and to improve veterinary services to avoid exposure of pigs to Trichinella.

Experimental Infection with Toxocara cati in BALB/c Mice, Migratory Behaviour and Pathological Changes

Experimental inoculations of 1000 Toxocara cati larval eggs were carried out in 18 BALB/c mice. The T. cati eggs used for inoculation were collected from the faeces of naturally infected cats. Euthanasia was performed on two mice on days 1, 2, 3, 4, 5, 6, 14, 21 and 28 post‐inoculation (p.i.). Tissue samples were taken for digestion and histopathology. Larvae were recovered from all infected mice and the average of all larvae recovered was 28.3% (95%; CI: 14.1–42.4). Maximum number was obtained from liver on days 1 and 2 p.i.; from the lung on day 2 p.i. and from the brain on day 28 p.i. In muscle, the recovery was high as from day 3 p.i., with the maximum obtained on day 28 p.i. Superficial foci of congestion and haemorrhage were macroscopically observed in the lungs between days 2 and 5 p.i. and in the brain between days 3 and 6 p.i. Microscopic lesions were observed in the liver between days 2 and 14 p.i., with periportal and subcapsule inflammatory infiltrates. In the lungs, haemorrhages and inflammatory infiltrates can be observed in the alveolar parenchyma, close to bronchioles and large blood vessels. In the brain, congestive areas without inflammatory reactions were seen. In muscle, the presence of inflammatory infiltrates and degenerated muscle can be observed surrounding a parasite larva. These same lesions were observed in myocardium and pericardium. The kidneys were congested with inflammatory infiltrates. The inflammatory cells present in all the tissues studied were lymphocytes, neutrophils and a few eosinophils. Formation of granulomas or signs of larva encapsulation were not observed. The migratory pattern of T. cati larvae in BALB/c mice and its tendency to become concentrated in the muscle reinforce the importance of the mouse as a paratenic host for the parasite’s cycle in the environment.

Evaluation of the risk of transmission of Trichinella in pork production systems in Argentina

Recently, there has been interest in programs that certify pork production practices that minimize the risk of exposure of pigs to Trichinella spiralis. Certification might be useful for reducing the risk of human trichinellosis from pork in Argentina, but more information is needed on pig production practices and sources of Trichinella infection in Argentinian pigs. In this study, 21 pig farms were assessed for Trichinella infection including some farms using total and partial confinement management, and others with pigs raised exclusively outdoors. A total of 3224 muscle samples were collected from pigs raised on these farms and tested to determine the presence of T. spiralis larvae by artificial digestion. Serum samples from the same 3224 pigs were tested for antibodies to T. spiralis by ELISA. For each farm, a questionnaire was completed summarizing information about management factors and this information was used to assess risk factors for exposure of T. spiralis. Based on the results, pigs raised outdoors were more likely to be infected than pigs raised in total or partial confinement (p< or =0.05). Pigs fed waste products containing meat were 12.5 times more likely to be infected than pigs not fed waste containing meat (p<0.01). The role played by rats in transmission of Trichinella is unclear; however, on farms with evidence of wild animals and access of pigs to wildlife carcasses, the prevalence of Trichinella infection was significantly higher. All pigs raised under good hygienic and sanitary conditions were negative for Trichinella infection by both artificial digestion and ELISA.

Prevalence of canine dirofilariosis in the City of Buenos Aires and its outskirts (Argentina)

During the past 10 years, the prevalence of canine dirofilariosis in the City of Buenos Aires and its outskirts, particularly in the northern and southern areas, has increased significantly. In the present work, studies were carried out in dogs living in the city and in its northern, western and southern outskirts from 1997 to 2001. For this purpose, 782 blood samples were collected and analyzed to determine circulating antigen, processed with the Witness Merial antigen test. The samples resulted in negative tests for subjects who lived in the city; however, 17.7 and 23.5% of the tests were positive from the northern and southern outskirts, respectively. When analyzed by sex, positive results were distributed as follows: 62.5% males and 37.5% females (P<0.05). No significant statistical difference was found on comparing purebred and cross-breds (P<0.05). It is interesting to point out the geographical distribution of the disease, which confirms that ecological factors such as water currents, abundant vegetation and the existence of mosquitoes all year round, are important for the biological cycle of Dirofilaria immitis.

Susceptibility of chickens (Gallus gallus domesticus) to Trichinella patagoniensis

Trichinella spp. is a genus of parasites that is widespread all over the world. In Argentina, T. spiralis was for years the only species involved in human and animal outbreaks. During the last decade, T. patagoniensis, a new Trichinella species, was discovered in Argentina. Up to now, this species has only been found in cougars (Puma concolor). Experimental infections in pigs, cats, mice and rats with this new genotype showed that cats and mice were the most susceptible hosts. The aim of the present work was to evaluate the susceptibility of chickens to infection with T. patagoniensis. In order to study the intestinal and muscular phase, and the histopathological changes, 27 Leghorn chickens were inoculated per os with 1000 muscle larvae of T. patagoniensis and were euthanized on days 4, 5, 6, 7, 11, 14, 21, 28 and 35. Adult worms of T. patagoniensis were recovered from the small intestine of chickens up to day 14p.i. Gross examination of small intestine showed a moderate congestive appearance. Microscopically, an inflammatory response with lymphocytes and eosinophils in lamina propria, slight hyperemia, oedema and some haemorrhagic areas were detected. Lesions observed in chickens were similar to those described in different animal species during the intestinal phase. No muscular larvae were recovered from the muscle samples. These results suggest that T. patagoniensis is not capable to complete its entire life cycle in chickens.

Evaluación de la transmisión galactógena de Trichinella patagoniensis en ratones BALB/c

Since 1916 to date, it has been suspected that vertical transmission of parasites from the genus Trichinella could occur in pregnant or lactating women during the parenteral phase of infection. The aim of the present study was to evaluate the transmammary transmission of T. patagoniensis in BALB/c mice. Twenty 7-week-old BALB/c mice were distributed into two groups of 10 individuals each, depending on the time of gestation when they were infected, 15 or 18 days after detection of the vaginal plug. Each group was subdivided into two subgroups of 5 mice each, which were given an oral dose of 100 or 500 infective larvae respectively. Euthanasia and subsequent artificial digestion was performed in the pups and the dams. No T. patagoniensis L1 larvae were found in any of the offsprings analyzed. The observed results suggest that vertical transmission of T. patagoniensis would not be possible in BALB/c mice.

EXPERIMENTAL INFECTION WITH Toxocara cati IN PIGS: MIGRATORY PATTERN AND PATHOLOGICAL RESPONSE IN EARLY PHASE

Experimental inoculations of approximately 100,000 infective Toxocara cati larval eggs were done in twelve pigs. The T. cati eggs used for inoculation were collected from cats feces. Another group of three pigs served as an uninfected control. Groups of infected pigs were euthanized at seven, 14, 21, and 28 days post-inoculation (dpi). Tissue samples were taken for digestion and histopathology changes in early phase. The number of larvae recovered from the lungs peaked at seven and 14 dpi and were also present at 21, and 28 dpi. Larvae of T. cati were present in the lymph nodes of the small and large intestine at seven, 14, and 28 dpi and at seven, 14, 21, and 28 dpi respectively. In other studied tissues, no larvae or less than one larva per gram was detected. The pathological response observed in the liver and lungs at seven and 14 dpi, showed white spots on the liver surface and areas of consolidation were observed in the lungs. The lungs showed an inflammatory reaction with larvae in center at 28 dpi. In the liver we observed periportal and perilobular hepatitis. The lymph nodes of the intestines displayed eosinophil lymphadenitis with reactive centers containing parasitic forms in some of them. The granulomatous reaction was not observed in any tissues. The role of the other examined tissues had less significance. The relevance of this parasite as an etiological agent that leads to disease in paratenic hosts is evident.

Estudio preliminar sobre los distintos estadios de Toxocara cati en gatos

PRELIMINARY STUDY ON THE DIFFERENT STAGES OF Toxocara cati IN CATS Toxocara cati larvae are able to migrate through the tissues of the cat, remaining infective. The objective of this study was to determine the presence of different stages of T. cati in naturally infected cats. Twelve cats found dead in the street were necropsied and samples of faeces were collected for coproparasitological analysis. Samples of muscle, the lungs, kidneys, liver, mammary gland and brain were removed. They were processed by the rapid artificial digestion technique to detect T. cati larvae. Coproparasitological analysis was positive for T. cati by 25%, to Toxascaris leonina at 16, 66% and 8.33% to both species. The 50% of animals presented adult parasites of T. cati, of which 20% were positive to T. leonina. Statistically significant differences were found between the presence of adult parasites and cat’s age. No statistically significant differences were observed in regard to sex. No larvae of T. cati were recovered from tissues. The differences in the results obtained between the coproparasitological technique and the necropsy could be due to the presence of immature stages of the parasites or to intermittent elimination of eggs in faeces. The absence of larvae in tissues raises several questions related to the migratory behaviour of T. cati larvae. Increasing the number of felines studied will contribute to ensure the validity of the results and will provide a better understanding about the behavior of T. cati larvae during the migratory phase in the cat.

Larval development of Aelurostrongylus abstrusus in experimentally infected Rumina decollata snails

Aelurostrongylus abstrusus is a lungworm distributed worldwide that affects wild and domestic cats, causing bronchopneumonia of varying intensity. Snails serve as intermediate hosts. The aim of the present study was to assess the larval development of A. abstrusus in R. decollata snails and to investigate its potential as an intermediate host. For this purpose, first-stage larvae (L1) of A. abstrusus were obtained from the faeces of naturally infected cats. Doses of 500 L1/snail were given to 24 R. decollata snails, placed on the soil of the breeder chamber, and maintained under laboratory conditions. Three snails were killed at 8, 10, 12, 16, 22, 26, 45 and 55 days post-infection (dpi), and the muscular foot and visceral body were separately digested by an artificial digestion technique. The morphometric parameters of different larval stages were recorded. The mean number of larvae reaching the infective stage at the end of the study (L3) was 262 larvae/snail. The greatest development to L3 was recorded from days16 to 55 pi, during which the isolation was maximum. A. Abstrusus L3 were isolated from the viscera, but isolation from the snail foot was significantly higher. Our results showed for the first time the ability of A. Abstrusus larvae to develop in R. decollata, thus serving as a potential intermediate host.