Red and fallow deer determine the density of Ixodes ricinus nymphs containing Anaplasma phagocytophilum

Background The density of Ixodes ricinus nymphs infected with Anaplasma phagocytophilum is one of the parameters that determines the risk for humans and domesticated animals to contract anaplasmosis. For this, I. ricinus larvae need to take a bloodmeal from free-ranging ungulates, which are competent hosts for A. phagocytophilum. Methods Here, we compared the contribution of four free-ranging ungulate species, red deer (Cervus elaphus), fallow deer (Dama dama), roe deer (Capreolus capreolus), and wild boar (Sus scrofa), to A. phagocytophilum infections in nymphs. We used a combination of camera and live trapping to quantify the relative availability of vertebrate hosts to questing ticks in 19 Dutch forest sites. Additionally, we collected questing I. ricinus nymphs and tested these for the presence of A. phagocytophilum. Furthermore, we explored two potential mechanisms that could explain differences between species: (i) differences in larval burden, which we based on data from published studies, and (ii) differences in associations with other, non-competent hosts. Results Principal component analysis indicated that the density of A. phagocytophilum-infected nymphs (DIN) was higher in forest sites with high availability of red and fallow deer, and to a lesser degree roe deer. Initial results suggest that these differences are not a result of differences in larval burden, but rather differences in associations with other species or other ecological factors. Conclusions These results indicate that the risk for contracting anaplasmosis in The Netherlands is likely highest in the few areas where red and fallow deer are present. Future studies are needed to explore the mechanisms behind this association.

Red and Fallow Deer Determine the Density of Ixodes Ricinus Nymphs Containing Anaplasma Phagocytophilum

Background: The density of Ixodes ricinus nymphs infected with Anaplasma phagocytophilum is one of the parameters that determines the risk for humans and domesticated animals to contract anaplasmosis. For this, I. ricinus larvae need to take a blood meal from free-ranging ungulates, which are competent hosts for A. phagocytophilum.Methods: Here, we compared the contribution of four free-ranging ungulate species, red deer (Cervus elaphus), fallow deer (Dama dama), roe deer (Capreolus capreolus), and wild boar (Sus scrofa) to A. phagocytophilum infections in nymphs. We used a combination of camera and live trapping to quantify the relative availability of vertebrate hosts to questing ticks in nineteen Dutch forest sites. Additionally, we collected questing I. ricinus nymphs and tested these for the presence of A. phagocytophilum. Furthermore, we explored two potential mechanisms that could explain differences between species: 1) differences in larval burden, which we based on data from published studies, and 2) differences in associations with other, non-competent hosts.Results: Principal component analysis indicated that the density of A. phagocytophilum infected nymphs (DIN) was higher in forest sites with high availability of red and fallow deer, and to a lesser degree roe deer. Initial results suggest that these differences are not a result of differences in larval burden, but rather differences in associations with other species or other ecological factors.Conclusions: These results indicate that the risk for contracting anaplasmosis in the Netherlands is likely highest in the few areas where red and fallow deer are present. Future studies are needed to explore the mechanisms behind this association.

Ascaris lumbricoides and Ascaris suum vary in their larval burden in a mouse model

Ascariasis is a neglected tropical disease, caused by Ascaris lumbricoides, affecting 800 million people worldwide. Studies focused on the early stage of parasite infection, occurring in the gut, liver and lungs, require the use of a mouse model. In these models, the porcine ascarid, Ascaris suum, is often used. The results obtained from these studies are then used to draw conclusions about A. lumbricoides infections in humans. In the present study, we sought to compare larval migration of A. suum and A. lumbricoides in mouse models. We used a previously developed mouse model of ascariasis, which consists of two mouse strains, where one mouse strain – C57BL/6J – is a model for relative susceptibility and the other – CBA/Ca – for relative resistance. Mice of both strains were infected with either A. suum or A. lumbricoides. The larval burden was assessed in two key organs, the liver and lungs, starting at 6 h post infection (p.i.) and ending on day 8 p.i. Additionally, we measured the larval size of each species (μm) at days 6, 7 and 8 p.i. in the lungs. We found that larval burden in the liver is significantly higher for A. lumbricoides than for A. suum. However, the inverse is true in the lungs. Additionally, our results showed a reduced larval size for A. lumbricoides compared to A. suum.

Immune humoral response of young lambs naturally infested by Oestrus ovis (Diptera: Oestridae)

Twenty-six newborn lambs were evaluated for 21 weeks, from birth to slaughter, to assess their plasma anti-Oestrus ovis immunoglobulin (IgG) using the ELISA technique. On the last day of sampling, all the lambs were slaughtered and O. ovis larvae were recovered, quantified and identified according to the larval stage. High levels of IgG were observed over the first three weeks of life, thus indicating that antibodies are transferred via colostrum from ewes to lambs. Afterwards, the antibody levels declined progressively until the lambs were 11 weeks of age and subsequently started to increase again when they were around 13 weeks of age, reaching the apex on the last week of sampling. All the lambs were parasitized with different larval stages of O. ovis, with an average of 39 larvae per lamb, and the intensity of the infestation ranged from 10 to 97 larvae. However, there was non-significant correlation coefficients between IgG levels and O. ovis larval burden (P > 0.05). In conclusion, although the lambs became infested with O. ovis at an early age, the larval burden was not associated with specific IgG levels.

Meriones unguiculatus infected by Haemonchus contortus: evaluation of different experimental protocols

Many important studies on resistance reversion, anthelmintic efficacy and, especially, new molecules with antiparasitic effects are performed in laboratories using gerbils (Meriones unguiculatus) as the experimental model. This study aimed to evaluate the use of corticosteroids (dexamethasone and methylprednisolone acetate) in gerbils experimentally infected with different doses of infective larvae (sheathed or exsheathed) of Haemonchus contortus. In the first experiment, 28 gerbils were divided into seven groups infected by 2–6 × 103 larvae, with or without immunosuppression using corticosteroids. In the second experiment, eight gerbils were divided into two groups infected by 2 × 103 sheathed or exsheathed larvae. For the third assay, seven immunosuppressed gerbils were infected with 2 × 103 sheathed larvae and were killed 15 days post infection (PI). The highest number of parasites was recovered from methylprednisolone-immunosuppressed animals. We observed red and white blood cell alterations and biochemical parameters in infected animals that had undergone immunosuppression with methylprednisolone. We highlight that in the first and second experiments a satisfactory number of worms was recovered using sheathed larvae and immunocompetent animals. When exsheathed larvae were used, the number of worms recovered was unsatisfactory. A considerable larval burden was recovered from immunosuppressed gerbils 15 days PI, and body weight did not influence establishment of larvae.

Prevalence and intensity of Oestrus ovis in sheep and goats in south-eastern part of Turkey

Oestrosis is a parasitic disease which is prevalent among sheep and goats in Mediterranean region. Slaughter house surveys to determine the prevalence and intensity of infestation by Oestrus ovis Linnaeus (Diptera: Oestridae) in sheep and goats, were conducted monthly for one year in south-eastern region of Turkey. A total of 804 heads belonging to 724 sheep and 80 goats were examined for Oestrus ovis larvae between May 2014 and April 2015. 72.75% of sheep heads and 50% of goat heads were seen to be infested with Oestrus ovis larvae. Of a total of 4723 larvae found in sheep heads, 2245 were detected to be first instars larva, 1231 second instars larva, 1247 third instars larva. Of a total of 259 larvae detected in goats, 150 were first instars larva, 79 second instars larva, 30 third instars larva. The mean of larval burden per infested animal was significantly higher in sheep (8.8±5.9) than in goat (6.5±5.0) (P less than 0.05). Monthly distribution of first, second and third instars larvae indicate that adult flies are active between April and end of September, first instars larvae enter hypobiotic period in October. In conclusion, it was revealed that to use an effective drug against Oestrus ovis that will be done during reproductive period of flies should start in April and continue until the end of summer due to high rates of oestrosis, parasite treatment that will be done when reproductive period ends should be done in October and November in the southeast part of Turkey.

Cascading effects of predator activity on tick-borne disease risk

Predators and competitors of vertebrates can in theory reduce the density of infected nymphs (DIN)—an often-used measure of tick-borne disease risk—by lowering the density of reservoir-competent hosts and/or the tick burden on reservoir-competent hosts. We investigated this possible indirect effect of predators by comparing data from 20 forest plots across the Netherlands that varied in predator abundance. In each plot, we measured the density of questing Ixodes ricinus nymphs (DON), DIN for three pathogens, rodent density, the tick burden on rodents and the activity of mammalian predators. We analysed whether rodent density and tick burden on rodents were correlated with predator activity, and how rodent density and tick burden predicted DON and DIN for the three pathogens. We found that larval burden on two rodent species decreased with activity of two predator species, while DON and DIN for all three pathogens increased with larval burden on rodents, as predicted. Path analyses supported an indirect negative correlation of activity of both predator species with DON and DIN. Our results suggest that predators can indeed lower the number of ticks feeding on reservoir-competent hosts, which implies that changes in predator abundance may have cascading effects on tick-borne disease risk.

Heavy metal intoxication compromises the host cytokine response in Ascaris Suum model infection

SummaryLead (Pb), Cadmium (Cd) and Mercury (Hg) are recognized for their deleterious effect on the environment and immunity where subsequently compromised immune response affects the susceptibility to the potential parasitic infections. This study examined the host cytokine response after heavy metal intoxication (Pb, Cd, and Hg) and subsequent Ascaris suum infection in BALB/c mice. Pb modulated murine immune response towards the Th2 type of response (delineated by IL-5 and IL-10 cytokine production) what was also dominant for the outcome of A. suum infection. Chronic intoxication with Pb caused a more intensive development of the parasite infection. Cd stimulated the Th1 immune response what was associated with increase in IFN-γ production and reduction of larvae present in the liver of intoxicated mice. The larval burden was also low in mice intoxicated with Hg. This was probably not related to the biased Th1/Th2 type of immune response, but rather to the bad host conditions caused by mercury toxicity and high level of pro-cachectic cytokine TNF-α.