Evaluation of the infectivity and the persistence of Trichinella patagoniensis in muscle tissue of decomposing guinea pig (Cavia porcellus).

Trichinella patagoniensis, a new species of Trichinella, is widespread in Argentina. The success of parasite transmission depends, among other factors, on the resistance of L1 larvae present in the muscle tissue (ML) of dead hosts undergoing the decomposition process in different environmental conditions. The aim of the present work was to study the infectivity of T. patagoniensis muscle larvae in Cavia porcellus and the capability of the parasite to survive in decomposed muscle tissue of guinea pigs subjected to different environmental conditions. Thirty-two female Ssi:AL guinea pigs were orally inoculated with 2000 ML of T. patagoniensis (ISS2311). All the animals were sacrificed 42 days post-infection. Twenty-six animals were eviscerated, and carcasses were placed on the surface of soil inside plastic boxes that were exposed to environmental conditions in the summer 2014-2015 and autumn of 2015 in Buenos Aires, Argentina. Carcasses from six animals were placed into a plastic box inside the refrigerator at a temperature of 4 °C. The muscle tissue samples from the carcasses were examined weekly for the presence of larvae, and the infectivity of recovered ML was tested in BALB/c mice. Our results showed for the first time the ability of T. patagoniensis to complete its life cycle in guinea pigs, thus serving as a potential natural host. Also, larvae of T. patagoniensis remained infective in muscle tissue for several weeks while undergoing decomposition under different environmental conditions.

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.

A Toxocara cati eggs concentration method from cats' faeces, for experimental and diagnostic purposes.

Toxocariosis is a zoonotic parasite infection worldwide distributed, now considered a neglected disease associated to poverty. For experimental infection in animals and to develop the diagnosis in humans it is necessary to obtain large number of Toxocara spp. larval eggs. Toxocara cati eggs recovered percentage from faeces of infected cats was determined employing a novel egg concentration method. The McMaster egg counting technique and the concentration method were applied on 20 positive cats' sample faeces obtained from naturally infected cats. The mean percentage of eggs recovered by the concentration method was 24.37% higher than the count obtained by McMaster egg counting technique. The main advantage of this method is that it can be obtained a small final volume with a high number of recovered eggs and a good quality inoculum for experimental and diagnostic purposes.

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.

Clinical, haematological, biochemical and economic impacts of Trichinella spiralis infection in pigs.

The purpose of this work was to assess the clinical, haematological and biochemical responses of pigs experimentally inoculated with Trichinella spiralis. Groups of three pigs were inoculated per os with 100, 500 and 5000 T. spiralis muscle larvae, two pigs were used as control. Clinical evaluation of disease in pigs included daily examination, rectal temperature measurements and cardiac and respiration rates. Haematological studies included: hematocrit (%), hemoglobin (g/dl), and white cell, neutrophil, lymphocyte and eosinophil counts. Blood biochemistry included: bun (mg/dl), creatinine (mg/dl), AST (UI/l), ALT (UI/l), CPK (UI/l) and ALP (UI/l). No significant differences were observed in rectal temperature and in cardiac and respiration rates between inoculated animals and the control group (p> or =0.05). Significant differences were detected (p< or =0.05) in the values of % hemoglobin, and eosinophils, as well as in the values of CK, ALP, AST and ALT. The variations observed in some cases were related to the number of T. spiralis larvae inoculated and varied with the number of days post-infection. Inoculated pigs showed significant differences (p< or =0.05) in weight gain when compared with uninoculated controls. This study has clinical, haematological, and enzyme alterations in Trichinella infected pigs provides a better understanding of acute and chronic trichinellosis in pigs.

Prevalence of Toxocara cati and other parasites in cats' faeces collected from the open spaces of public institutions: Buenos Aires, Argentina.

Toxocarosis is a worldwide parasitic infection that affects both cats and dogs. Toxocara cati (Schrank, 1788) syn. Toxocara mystax (Zeder, 1800) prevalence was studied in faeces from stray cats collected from the open spaces of public institutions of Buenos Aires city, both building and surrounding open spaces are fenced off. Of the 465 samples obtained from March to June of 2005, 58.3% were found to have parasite eggs. The following parasites were identified from the 271 positive samples: T. cati (61.2%), Cystoisospora spp. (20.3%), Trichuris spp. (17.0%), Toxascaris leonina (15.1%), Ancylostoma spp. (14%) and Aelurostrongylus abstrusus (2.6%). T. cati prevalence was 35.7% (95% confidence interval: 31.2-40.1), with a 42.2% single isolations. The most frequent combination was T. cati and Cystoisospora spp. (9%). More than half the areas studied showed over 40% prevalence. Seventy-one percent of the collected samples were fresh with a variable moist consistency and 29% were older with a dry consistency. A statistically significant association was found between sample consistency and presence of parasites (chi2 = 10.81; p = 0.001) as also between sample consistency and presence of T. cati (chi2 = 11.27; p = 0.0007). Moist consistencies were significantly different from the rest: consistency (wet or dry) versus parasites (z = 1.95; p = 0.02) (95% confidence interval: 0.004-0.203); consistency (wet or dry) versus T. cati (z = 3.25; p = 0.0006) (95% confidence interval: 0.075-0.254). The cat population that inhabits these public green spaces contaminates the environment, thus transforming them into dangerous spaces with a variable rate for the human population that spends time in these places.

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.