Experimental transmission of Toxocara canis from Blattella germanica and Periplaneta americana cockroaches to a paratenic host.

The present study assessed the capacity of Blattella germanica and Periplaneta americana to disseminate and transmit infective phases of T. canis to rats, which were used as a model paratenic host. P. americana and B. germanica inoculated orally with T. canis larvated eggs shed eggs and larvae in their fecal matter during the first 6days post-inoculation. Larvae were recovered from the brain, lungs, kidneys and liver of rats that had been inoculated with either infected cockroaches or their feces. ELISAs of serum detected an increase of antibodies anti-T. canis excretion-secretion antigens, whereas Western Blot (WB) showed 4 bands (120, 50, 35 and 28kDa) that were similar to those found in positive control rats. Macroscopically, the liver and kidneys of infected rats had hemorrhagic areas with milk-spot-like lesions. The lungs showed diffuse grey protuberances. Histologically, hemorrhagic areas with leucocytic infiltrate were observed in the liver, lungs and kidneys. Some larvae were found within a granuloma that was surrounded by eosinophils and other leucocytic infiltrates. Larvae were found in the brain, but without inflammatory infiltrate. Both cockroach species that ingested larvated eggs of T. canis may shed viable larvae or eggs in their fecal matter. The induction of specific serum antibodies, presence of larvae in tissues and characteristic lesions associated with larval migration in the organs of rats that had ingested either whole adults or feces of B. germanica or P. americana demonstrate the capacity of these cockroaches to transmit toxocariosis to paratenic hosts.

Progesterone inhibits the in vitro L3/L4 molting process in Haemonchus contortus.

We evaluated the direct effects of progesterone on the morphology, maturation and behavior of Haemonchus contortus larvae in vitro. The presence and location of possible progesterone receptors in these larvae were also determined. The addition of 8ng/mL of progesterone to larval cultures over 10days reduced larval enlargement, while the addition of 160ng/mL of the hormone increased the enlargement. Up to 62% and 65% of the H. contortus larvae molted from third-stage larvae (L3) to fourth-stage larvae (L4) when cultured in RPMI-1640 media without hormone for 5 and 10days, respectively. The addition of different progesterone concentrations (1, 8, 16, 80 and 160ng/mL) to the larval cultures significantly inhibited the molting process within the same periods. The addition of 8ng/mL or higher progesterone concentrations to the cultures significantly increased larval motility (p<0.05) compared with unstimulated larvae. Flow cytometry showed the expression of progesterone receptors (P4-R) in 15% of the cells from newly isolated H. contortus larvae. When the larvae were cultured for 5days in the presence of the hormone, the percentage of P4-R+ cells remained the same. In contrast, unstimulated larvae showed a significant reduction in the number of P4-R+ cells. Using confocal microscopy, a greater concentration of P4-Rs was immunolocated in the anterior portion of the alimentary tract of the larvae, suggesting that the cells in this region are targeted by the hormone. The results of the present study show that H. contortus larvae have possible P4-Rs and respond to this hormone by inhibiting their molting process, thereby suggesting the participation of progesterone in the larval arrest phenomenon.

Partial protection and abomasal cytokine expression in sheep experimentally infected with Haemonchus contortus and pre-treated with Taenia hydatigena vesicular concentrate.

The abomasal expression of IL-2, IL-4, IL-6, IL-10 and IFNγ in lambs experimentally infected with Haemonchus contortus and its relationship to protection induced by a Taenia hydatigena larvae vesicular concentrate (ThLVC) were evaluated. The lambs that were only infected with H. contortus larvae showed a worm burden greater (p<0.05) than the lambs that received ThLVC prior to infection. Moreover, the lambs that received ThLVC showed a greater (p<0.05) number of blood eosinophils than the lambs that did not receive the ThLVC. In general, the lambs that received ThLVC prior to infection had a greater amount of eosinophils and mast cells and higher in situ expression of IFNγ, IL-2, IL-4, IL-6 and IL-10 in the abomasal wall than the lambs that were infected with H. contortus only or that received ThLVC (p<0.05) only. A higher expression of IL-2 and IFNγ in the submucosa compared to the abomasal mucosa and a higher expression of IL-4 in the abomasal mucosa compared to the submucosa was observed (p<0.05). These results suggest that there is a Th1 type response in the abomasal submucosa and a Th2 type response in in the abomasal mucosa. The amount of eosinophils and mast cells and the in situ expression of IFNγ, IL-2, IL-4 and IL-6 in the abomasal walls were negatively correlated with the worm burden (p<0.05). These results suggest that ThLVC is a non-specific immune stimulator for the abomasal immune response, and it is likely that the protection observed is the result of this effect.

Differential immune response between fundic and pyloric abomasal regions upon experimental ovine infection with Haemonchus contortus.

The effect of experimental haemonchosis on the number of tissue eosinophils, plasma cells and lymphocyte subpopulations was evaluated in the fundic abomasal region, the pyloric abomasal region and the abomasal lymph node of Blackbelly lambs, which are resistant to infection, and Columbia lambs, which are susceptible to infection. An increase in the number of tissue eosinophils and CD4+ and WC1(+)γδ T-cells was observed in the pyloric abomasal region of Blackbelly lambs and correlated with lower worm burden and greater resistance to infection. Increases in IgA+ plasma cells from the pyloric abomasal region were observed in both infected groups, but there was no difference between the groups. Therefore, increases in IgA+ plasma cells did not explain the resistance observed. Infection caused a significant increase in tissue eosinophils in the abomasal lymph node of Blackbelly lambs and a decrease in the number of CD4+ T-cells in lambs of both breeds. CD8+ T-cells and IgG+ and IgM+ plasma cells were not associated with either infection or resistance. In this work, clear differences were observed in the numbers of CD4+ and WC1(+)γδ T-cells, tissue eosinophils and IgA+ plasma cells between the abomasal regions studied. These differences indicate that the immunological response is not homogenous in all abomasal mucosa and that evaluating the response from a single abomasal region may not be representative of the cellular response across the abomasum.

Anthelmintic resistance in sheep farms: update of the situation in the American continent.

The present paper reviews the frequency of anthelmintic resistance in sheep farms in different countries of the American continent and describes some aspects that might influence the trend in sheep farms. The situation of anthelmintic resistance in sheep farms has been explored mainly in south of the continent (Argentina, Brazil and Uruguay) where sheep farming is an important industry. In those three countries, as well as in Paraguay, the first comprehensive surveys of anthelmintic resistance were performed among countries in the continent, which showed evidence of high frequency of sheep farms with anthelmintic resistance. Today, it is common to find sheep flocks with multiple-resistant worms. In North and Central America, a similar situation has been reported in sheep farms in the south of the United States of America, parts of Mexico and Costa Rica. On the other hand, other areas of the continent show low frequency of farms with anthelmintic resistance. From many areas no results have been published regarding situation on anthelmintic resistance or, alternatively, published results have received limited dissemination. Although the diagnosis of anthelmintic resistance is important for decision making of helminth management/control at the farm level, this is still an aspiration rather than a reality. For decades, researchers working on anthelmintic resistance in the American continent have expressed the need to change farmers' attitudes towards anthelmintic drugs. A common advice has been to check the anthelmintic drug efficacy regularly and reduce the dependence on these with alternative control measures. In spite of such advice, the challenge to stop/delay the advancement of anthelmintic resistance against the available anthelmintic drugs is still present. The evidence suggests that anthelmintic resistance is a growing phenomenon in the American continent. The situation described might be the tip of the iceberg, as anthelmintic resistance is still largely under-diagnosed. Hence, a different approach to tackle the advancement of anthelmintic resistance in sheep farms must be found. Awareness of farmers on the importance of diagnosis of anthelmintic resistance is not enough. Technical support schemes that provide the diagnostic service cheaply and timely must be implemented together with the research aiming at the adoption of control methods to reduce the dependence on conventional anthelmintic drugs. Unless these elements are readily available for producers, the negative consequences of anthelmintic resistance on sheep farming in America will continue to worsen with time.

Decrease in establishment of Haemonchus contortus caused by inoculation of a Taenia hydatigena larvae vesicular concentrate.

The effect of Taenia hydatigena larvae vesicular concentrate (ThLVC) on the establishment of an experimental infection by Haemonchus contortus was evaluated. The lambs that received ThLVC showed a greater (P<0.05) average of blood eosinophils (BE) than the lambs that did not receive ThLVC. Lambs that were only infected with H. contortus larvae showed a fecal egg count (FEC) and an adult phase (AP) number greater (P<0.05) than lambs that received ThLVC prior to infection. No effect was observed in size and prolificacy of AP after the administration of ThLVC. The infection with H. contortus caused an increase (P<0.05) in CD4+ lymphocytes in abomasal lymph node (ALN) and the combination of ThLVC plus the infection with H. contortus caused an increase (P<0.05) in CD4+ lymphocytes in the abomasal wall (AW). In addition, a positive correlation between gamma-delta lymphocytes of ALN (r=0.73, P<0.05) with the presence of AP in the abomasum was observed. The quantity of plasma cells in ALN and AW was not affected by the administration of ThLVC nor related to the resistance observed. The results shown in this work leave no doubt that ThLVC administration prior to inoculation produces eosinophilia and partially protects against the establishment of H. contortus. However, this protection is not only attributable to the role of eosinophils, since ThLVC can function stimulating other immune response cells, such as T lymphocytes, both contributing to prevent the presence of worms.