Inhibition of miR-99a-5p prevents allergen-driven airway exacerbations without compromising type-2 memory responses in the intestine following helminth infection.

Acute exacerbations (AE) of asthma, remain one of the biggest concerns for patients living with asthma. As such, identifying the causes, the molecular mechanisms involved and new therapeutic interventions to prevent AE is a high priority. Immunity to intestinal helminths involves the reactivation of type-2 immune responses leading to smooth muscle contraction and mucus hypersecretion-physiological processes very similar to acute exacerbations in the airways following allergen exposure. In this study, we employed a murine model of intestinal helminth infection, using Heligmosomoides polygyrus, to identify miRNAs during active expulsion, as a system for the identification of miRNAs that may contribute to AE in the airways. Concomitant with type-2 immunity and expulsion of H. polygyrus, we identified miR-99a-5p, miR-148a-3p and miR-155-5p that were differentially regulated. Systemic inhibition of these miRNAs, alone or in combination, had minimal impact on expulsion of H. polygyrus, but inhibition of miR-99a-5p or miR-155-5p significantly reduced house dust mite (HDM)-driven acute inflammation, modelling human acute exacerbations. Immunological, pathological and transcriptional analysis identified that miR-155-5p or miR-99a-5p contribute significantly to HDM-driven AE and that transient inhibition of these miRNAs may provide relief from allergen-driven AE, without compromising anti-helminth immunity in the gut.

Effect of co-infection with a small intestine-restricted helminth pathogen on oral prion disease pathogenesis in mice.

The early replication of some orally-acquired prion strains upon stromal-derived follicular dendritic cells (FDC) within the small intestinal Peyer's patches is essential to establish host infection, and for the disease to efficiently spread to the brain. Factors that influence the early accumulation of prions in Peyer's patches can directly influence disease pathogenesis. The host's immune response to a gastrointestinal helminth infection can alter susceptibility to co-infection with certain pathogenic bacteria and viruses. Here we used the natural mouse small intestine-restricted helminth pathogen Heligmosomoides polygyrus to test the hypothesis that pathology specifically within the small intestine caused by a helminth co-infection would influence oral prion disease pathogenesis. When mice were co-infected with prions on d 8 after H. polygyrus infection the early accumulation of prions within Peyer's patches was reduced and survival times significantly extended. Natural prion susceptible hosts such as sheep, deer and cattle are regularly exposed to gastrointestinal helminth parasites. Our data suggest that co-infections with small intestine-restricted helminth pathogens may be important factors that influence oral prion disease pathogenesis.

GUT PARASITE LEVELS ARE ASSOCIATED WITH SEVERITY OF RESPONSE TO IMMUNE CHALLENGE IN A WILD SONGBIRD.

Life history trade-offs have been posited to shape wild animals' immune responses against microparasites (e.g., bacteria, viruses). However, coinfection with gut helminths may bias immune phenotypes away from inflammatory responses and could be another mechanism underlying variation in immune responses. We examined how the magnitude of a common and costly response to microparasites, the acute phase response (APR), varied with helminth coinfection at both the individual and the population levels in Song Sparrows ( Melospiza melodia). The APR includes fever and sickness behaviors, like lethargy and anorexia, and provides a whole-organism metric of immune activation. We combined data on fever and lethargy in response to an immune challenge (lipopolysaccharide) with postmortem data assessing helminth burdens and data on malarial parasite infection from blood samples in sparrows from two populations: southern California and western Washington, US. We predicted that birds with higher helminth burdens would express less severe APRs, at both the individual and population levels. Furthermore, we predicted that these reduced immune responses would diminish resistance against malarial parasites and would thus be associated with higher prevalences of such parasites. Previously, Song Sparrows from Washington have been shown to mount less severe APRs than those from California. In our study, Washington birds also exhibited higher helminth burdens and a higher prevalence of one type of avian malarial parasite. Because of low variation in helminth burdens in California (median=0, range=0-3), we tested within-population relationships only in birds from Washington, where the severity of fever and lethargy correlated negatively with helminth burden. These results suggested that helminth coinfection could help mediate immune responsiveness in wild songbirds.

Is the infectiousness of dogs naturally infected with Trypanosoma cruzi associated with poly-parasitism?

Interactions among different species of parasites co-infecting the same host could be synergistic or antagonistic. These interactions may modify both the frequency of infected hosts and their infectiousness, and therefore impact on transmission dynamics. This study determined the infectiousness of Trypanosoma cruzi-seropositive dogs (using xenodiagnosis) and their parasite load (quantified by qPCR), and tested the association between both variables and the presence of concomitant endoparasites. A cross-sectional serosurvey conducted in eight rural villages from Pampa del Indio and neighboring municipalities (northeastern Argentina) detected 32 T. cruzi-seropositive dogs out of 217 individuals examined for infection. Both the infectiousness to the vector Triatoma infestans and parasite load of T. cruzi-seropositive dogs examined were heterogeneous. A statistically significant, nine-fold higher mean infectiousness was registered in T. cruzi-seropositive dogs co-infected with Ancylostoma caninum and a trematode than in T. cruzi-seropositive dogs without these infections. The median parasite load of T. cruzi was also significantly higher in dogs co-infected with these helminths. An opposite trend was observed in T. cruzi-seropositive dogs that were serologically positive to Toxoplasma gondii or Neospora caninum relative to dogs seronegative for these parasites. Using multiple logistic regression analysis with random effects, we found a positive and significant association between the infectiousness of T. cruzi-seropositive dogs and co-infections with A. caninum and a trematode. Our results suggest that co-infections may be a modifier of host infectiousness in dogs naturally infected with T. cruzi.

Toxoplasma gondii coinfection with diseases and parasites in wild rabbits in Scotland.

In wild rabbits (Oryctolagus cuniculus) on an estate in Perthshire, central Scotland, the seroprevalence of Toxoplasma gondii was 18/548 (3·3%). The wild rabbit could be a T. gondii reservoir and it has potential value as a sentinel of T. gondii in environmental substrates. Toxoplasma gondii was associated with female sex (P < 0·001) and with relatively heavy infections by Eimeria stiedae (P = 0·036). It was not associated with the intensity of coccidial oocysts, the severity of myxomatosis caused by the virus Myxomatosis cuniculi, the intensity of roundworm eggs, the year or season, rabbit age or distance from farm buildings. Coinfections could have been affected by gestational down regulation of type 1 T helper cells. A sudden influx or release of T. gondii oocysts might have occurred. This is the first report of T. gondii in any wild herbivore in Scotland and also the first report of lapine T. gondii as a coinfection with E. stiedae, M. cuniculi and helminths.

Mortality of American bullfrog tadpoles Lithobates catesbeianus infected by Gyrodactylus jennyae and experimentally exposed to Batrachochytrium dendrobatidis.

The fungal pathogen Batrachochytrium dendrobatidis (Bd), which causes the disease chytridiomycosis in postmetamorphic amphibians, has been linked to amphibian population declines. Different amphibian species, however, exhibit different susceptibility to Bd pathogenicity. At the same time, agricultural pesticides commonly found contaminating aquatic habitats have been reported to increase the susceptibility of amphibians to pathogens. To investigate whether certain pesticides are able to alter the pathogenicity of Bd to larval amphibians, we exposed larval American bullfrogs Lithobates catesbeianus to end-use formulations of the herbicides atrazine or glyphosate, and then exposed them to Bd. Following the experimental exposures, a preexisting infection of the tadpoles by the monogenean ectoparasite Gyrodactylus jennyae was detected in all experimental and control tadpoles. Gyrodactylus jennyae infection intensity varied, and individuals with heavy G. jennyae infections suffered more skin erosion due to grazing by the parasite. Tadpoles experimentally exposed to Bd, or to Bd and either herbicide, had significantly reduced survival rates compared with untreated tadpoles that were only infected by G. jennyae. Increased mortality was also correlated with degree of skin erosion; survival of tadpoles with severe skin erosion was significantly reduced compared with that of tadpoles with no, or mild, skin erosion. While infected with G. jennyae, the group of tadpoles with the lowest survival rate (exposed only to Bd) included significantly more individuals exhibiting severe skin erosion and significantly fewer individuals without skin erosion, compared with the control group. These results emphasize the potential pathogenicity of gyrodactylid infections in larval amphibian hosts and suggest that concomitant exposures to Bd may enhance infections and effects of G. jennyae in bullfrog tadpoles.

Anthelmintic and relaxant activities of Verbascum Thapsus Mullein.

BACKGROUND: Verbascum thapsus is used in tribal medicine as an antispasmodic, anti-tubercular agent and wormicide. In this study, we investigated the antispasmodic and anthelmintic activities of crude aqueous methanolic extract of the plant. METHODS: V. thapsus extracts were tested against roundworms (Ascaridia galli) and tapeworms (Raillietina spiralis). Each species of worm was placed into a negative control group, an albendazole treatment group, or a V. thapsus treatment group, and the time taken for paralysis and death was determined. In addition, relaxation activity tests were performed on sections of rabbit's jejunum. Plant extracts were tested on KCl-induced contractions and the relaxation activities were quantified against atropine. V. thapsus calcium chloride curves were constructed to investigate the mode of action of the plant extracts. RESULTS: We detected flavonoids, saponins, tannins, terpenoids, glycosides, carbohydrates, proteins, fats and fixed oils in V. thapsus. For both species of worm, paralysis occurred fastest at the highest concentration of extract. The relative index values for paralysis in A. galli were 4.58, 3.41 and 2.08, at concentrations of 10, 20 and 40 mg/ml of plant extract, respectively. The relative index for death in A. galli suggested that V. thapsus extract is wormicidal at high concentration. Similarly, the relative indexes for paralysis and death in R. spiralis suggested that the extract is a more potent wormicidal agent than albendazole. The mean EC(50) relaxation activity values for spontaneous and KCl induced contractions were 7.5 ± 1.4 mg/ml (6.57-8.01, n = 6) and 7.9 ± 0.41 mg/ml (7.44-8.46, n = 6), respectively. The relaxation activity of the extract was 11.42 ± 2, 17.0 ± 3, 28.5 ± 4, and 128.0 ± 7% of the maximum observed for atropine at corresponding concentrations. The calcium chloride curves showed that V. thapsus extracts (3 mg/ml), had a mean EC(50) (log molar [calcium]) value of -1.9 ± 0.06 (-1.87 - -1.98, n = 6) vs. control EC(50) = -2.5 ± 0.12 (-2.37 - -2.56, n = 6), whereas the verapamil (0.1 µM) EC(50) was -1.7 ± 0.1 (-1.6 - -1.8, n = 6) vs. control EC(50) = -2.4 ± 0.09 (-2.3 - -2.47, n = 5). CONCLUSIONS: Our results suggest that V. thapsus, which is currently used by some tribes in the Malakand region of Pakistan, has anthelmintic and antispasmodic value.

The effect of helminth co-infection on malaria in mice: a meta-analysis.

The question of how helminths may alter the course of concurrent malaria infection has attracted much interest in recent years. In particular, it has been suggested that by creating an anti-inflammatory immune environment, helminth co-infection may dampen both protective and immunopathological responses to malaria parasites, thus altering malaria infection dynamics and disease severity. Both synergistic and antagonistic interactions are reported in the literature, and the causes of variation among studies are not well understood. Here, meta-analysis of 42 mouse co-infection experiments was used to address how helminths influence malaria parasite replication and host mortality, and explore the factors explaining variation in findings. Most notably, this analysis revealed contrasting effects of helminth co-infection in lethal and resolving malaria models. Whilst co-infection exacerbated mortality and increased peak parasitaemia in ordinarily resolving malaria infections (Plasmodium chabaudi and Plasmodium yoelii), effects among lethal malaria infections (Plasmodium berghei) tended to be in the opposite direction with no change in parasitaemia. In the subset of experiments on cerebral malaria models (P. berghei ANKA strain in a susceptible host), helminth co-infection significantly delayed death. These findings are consistent with the hypothesis that depending on the existing balance of pro- and anti-inflammatory responses mounted against malaria parasites in a given host, immune responses elicited by helminth co-infection may either promote or inhibit malarial disease. However, despite such broad patterns, a prominent feature of this dataset was great heterogeneity in effects across studies. A key future challenge therefore lies in explaining the biological causes of this variation, including a more thorough exploration of non-immunological mechanisms of helminth-malaria interaction.

Fungal airsacculitis associated with multiple helminth infestations in a black-eared kite (Milvus migrans).

A young, female black-eared kite was rescued from a small reservoir adjacent to a rice paddy in Nagano Prefecture, Japan. The bird was given a fluid diet through the esophagus and started to eat by herself from the fifth day. Her fecal samples were examined for parasites on the seventh day and fluke eggs were detected. Capillaria and Ascarididae eggs were also detected from day 19 and day 32, respectively. The bird started to show loss of appetite from day 22 and finally showed no appetite on day 35. On day 38, the bird was treated with Profender Spot (Bayer Health Care, Tokyo, Japan) but died on day 41. A necropsy revealed a thickened air sac associated with considerable fungal growth. Histopathologic examination showed that the mucous membrane of the saccobronchus was thickened with hyphal proliferation, and the fungus was identified as Aspergillus fumigatus. A number of trematodes, thin nematodes, and four roundworms were obtained from the alimentary tract. Parasitologically, they were identified as Neodiplotomum pseudattenuatum, a Capillaria sp., and Porrocaecum phalacrocoracis, respectively. In conclusion, the bird was diagnosed as having fungal airsacculitis associated with multiple helminth infestations.

Parasitism and colic.

Equids are hosts to dozens of species of internal parasites that infect no other domestic animals. Virtually all horses, especially those exposed to pasture, experience some level of parasitism continuously. Despite pathologic evidence of parasitic damage in various organs and tissues, few parasitisms are manifested systemically in well-managed horses. Contrary to conventional wisdom, only three common parasitisms of horses are likely to be manifested as colic: Strongylus vulgaris, Parascaris equorum, and Anoplocephala perfoliata. This article discusses the life cycles, pathophysiology, manifestations and clinical findings, treatment, and management of these three common parasitisms. It also discusses related aspects of several other parasitisms that are unlikely to cause colic.

Could parasites destabilize mouse populations? The potential role of Pterygodermatites peromysci in the population dynamics of free-living mice, Peromyscus leucopus.

Peromyscus leucopus populations exhibit unstable population dynamics. Mathematical models predict instability with chronic parasite infections that reduce host fecundity when the parasite distribution within the host population is close to random. We examined the role the nematode Pterygodermatites peromysci may play in influencing the dynamics of these mice. There were seven gastrointestinal worms infecting mice. Pterygodermatites peromysci was the most prevalent and varied seasonally from 12.3% in November to 36.0% in July. Prevalence was higher in adults (30.8%) than juveniles (4.6%) and there were no statistical differences in prevalence or intensity between the sexes. Overall the distribution was random; the relationship between log variance and log mean of P. peromysci intensity from 17 sites was not significantly different from unity. There were significant relationships between infection and breeding condition, suggesting parasites could be the cause of reduced female breeding. A generalized linear model found the likelihood of P. peromysci infection in adults increased with body mass, the presence of other helminths, and when hosts were in breeding condition. Likewise, the intensity of infection was positively related to co-infections and body mass. Pterygodermatites peromysci infection was associated with the presence of the oxyurid nematode Syphacia peromysci but co-infection was lower in females than males. Amongst females, co-infection was greater when breeding, particularly during lactation. The P. peromysci age-intensity relationship increased with age and rose to an asymptote as expected for a parasite with constant mortality and no acquired immunity. Overall, P. peromysci had a random distribution and was associated with reduced breeding; we discuss how these destabilizing processes may influence the dynamics of P. leucopus.

Frequency of treatment and production performance using the FAMACHA method compared with preventive control in ewes.

The rapid escalation of anthelmintic resistance in parasites suggests the adoption of different strategies for parasite control in small ruminants instead of relying only on the use of chemicals. The integrated system of parasite control (SICOPA) program uses the FAMACHA method, which is used to separately identify sheep that are resistant/resilient or susceptible to Haemonchus contortus, or together with other management practices, such as pasture rotation or the monitoring of drug efficacy. The objective of this work was to compare two methods of parasite control in ewes. A flock of ewes (n=90) of Ile de France and Texel breeds was monitored from August 2001 to July 2003 under suppressive treatment (45-day treatment interval) and from August 2003 to July 2006 under the partial selective regimen based on FAMACHA evaluations. Fecal samples were collected for fecal egg counts (EPG) and larval identification to monitor infection during the 5-year period. After the partial selective evaluations, an average of 19% of the animals was treated each year between 2003 and 2006. The reproductive indexes of parturition (89%), birth rate (119%), lamb weight (4.1 kg) and lamb mortality (5.2%) were similar under the partial selective regimen and the previous suppressive treatment period. H. contortus was the most prevalent species, and EPG values were not statistically different across periods or among treatment regimes. The results demonstrate that the FAMACHA method allowed a large number of naturally infected ewes to be raised with reduced anthelmintic treatment without a negative impact on their reproductive indexes. It is indicated, though, that this method be applied together with other available strategies. Culling was based on clinical signs and ranged from 5.5 to 20% per year. The results suggest that an important host-specific effect may have regulated the rate of infection, expressing the resistant/resilient characteristic within the flock with an important economical benefit.

Infection and autoimmunity.

The development of some autoimmune diseases is increasing in the developed world faster than can be accounted for by genetic change. The development of these autoimmune diseases, such as Type 1 diabetes, is known to be influenced by both genetic and environmental factors. Environmental factors which have been considered to play a role include infectious agents such as viruses or bacteria. The search for a common initiating infection in the aetiology of Type 1 diabetes as proved thus far inconclusive. An alternative way of considering a role for infection is that infection may have historically prevented the development of autoimmune disease. In the developing world changes have occurred such that many chronic infections have been eliminated and this may have led to the emergence of autoimmune pathology. Evidence in support of this hypothesis is considered here and factors governing the development of autoimmunity compared with those which might have influenced the development of childhood leukaemia.

Interactions between macroparasites and microparasites drive infection patterns in free-ranging African buffalo.

Epidemiological studies typically focus on single-parasite systems, although most hosts harbor multiple parasite species; thus, the potential impacts of co-infection on disease dynamics are only beginning to be recognized. Interactions between macroparasites, such as gastrointestinal nematodes, and microparasites causing diseases like TB, AIDS, and malaria are particularly interesting because co-infection may favor transmission and progression of these important diseases. Here we present evidence for strong interactions between gastrointestinal worms and bovine tuberculosis (TB) in free-ranging African buffalo (Syncerus caffer). TB and worms are negatively associated at the population, among-herd, and within-herd scales, and this association is not solely the result of demographic heterogeneities in infection. Combining data from 1362 buffalo with simple mechanistic models, we find that both accelerated mortality of co-infected individuals and TB transmission heterogeneity caused by trade-offs in immunity to the two types of parasites likely contribute to observed infection patterns. This study is one of the first to examine the relevance of within-host immunological trade-offs for understanding parasite distribution patterns in natural populations.

Parasites prevent summer breeding in white-footed mice, Peromyscus leucopus.

Food and parasites can independently play a role in destabilizing population fluctuations of animals, and yet, more than 50 years ago, David Lack proposed that these two factors should act in concert. We examined the role of these factors on the vital rates of free-living white-footed mice (Peromyscus leucopus) over the summer and autumn months. We used a replicated factorial experiment in which deer exclosures doubled acorn availability and anthelmintic application reduced gastrointestinal helminths. Specifically, we wanted to know if either factor or an interaction between the two accounted for the midsummer breeding hiatus observed in this species. We found no influence of habitat quality on mouse breeding, vital rates, or demography; however, anthelmintic treatment resulted in mice continuing to reproduce during the hiatus at the same rate as previously, and they also exhibited increased body condition, growth rate, and survival. These results provide evidence that gastrointestinal helminths reduce P. leucopus reproductive output in central Pennsylvania, and these effects on reproduction could play a role in the unstable dynamics of small mammals.

Counter-regulatory anti-parasite cytokine responses during concurrent Plasmodium yoelii and intestinal helminth infections in mice.

Malaria and helminth infections are two of the most prevalent parasitic diseases globally. While concomitant infection is common, mechanisms contributing to altered disease outcomes during co-infection remain poorly defined. We have previously reported exacerbation of normally non-lethal Plasmodium yoelii malaria in BALB/c mice chronically infected with the intestinal trematode Echinostoma caproni. The goal of the present studies was to determine the effect of helminth infection on IFN-gamma and other key cytokines during malaria co-infection in the P. yoelii-E. caproni and P. yoelii-Heligmosomoides polygyrus model systems. Polyclonally stimulated spleen cells from both E. caproni- and H. polygyrus-infected mice produced significantly lower amounts of IFN-gamma during P. yoelii co-infection than malaria-only infected mice. Furthermore, the magnitude of IFN-gamma suppression was correlated with the relative amounts of IL-4 induced by these helminths (E. caproni=low; H. polygyrus=high), but not IL-10. Concurrent malaria infection also suppressed helminth-associated IL-4 responses, indicating that immunologic counter-regulation occurs during co-infection with malaria and intestinal helminths.

Studies on the interaction between Salmonella enterica ser. Typhimurium and intestinal helminths in pigs.

Concomitant infections with helminths and bacteria may affect the course and the resulting disease outcome of the individual infections. Salmonella, Oesophagostomum, Trichuris and Ascaris coexist naturally in pig herds in Denmark, and possible interactions were studied. Pigs in one experiment were trickle infected with low or moderate dose levels of Oesophagostomum spp. and challenge infected with S. Typhimurium. In another experiment, pigs were inoculated with S. Typhimurium followed by a challenge exposure to either Oesophagostomum, Trichuris or Ascaris. Enhancement of the Salmonella infection was not demonstrated in either experiment. The helminth effect on the pigs was modest and may explain the lack of influence on the Salmonella infection. A previous experiment with a larger Oesophagostomum infection level resulted in enhancement of the S. Typhimurium infection. A dose dependency of the interaction is therefore suggested. However, the relatively high worm burdens in the present study suggest that infection with these common pig helminths does generally not influence the course of concurrent S. Typhimurium infections under natural conditions.

Prevalence of large endoparasites at necropsy in horses infected with Population B small strongyles in a herd established in Kentucky in 1966.

Two closed horse herds (Old Lot 4 and Field 24), infected since 1966 with Population B small strongyles resistant to thiabendazole (TBZ) and phenothiazine (PTZ), were terminated in February, March, and May, 2005. At necropsy, only the large endoparasites were identified and counted. The number of horses on pasture was 14 (239 days of age to 23 years old) for Old Lot 4 and two (3 to 20 years old) for Field 24. The time of the last antiparasitic treatment, relative to the year (2005) of necropsy, was 26 years for Old Lot 4 and 9 years for Field 24 horses. Gasterophilus intestinalis third instars (three to 113 specimens/horse) were found in all 16 horses and second instars (one to two) in two horses. Gasterophilus nasalis third instars (one to three) were recovered from five horses. Parascaris equorum infections (23 to 144) were in four horses (239 days to 4 years old). Strongylus vulgaris were present in the large intestine (one to 155) of 13 horses from 239 days to 23 years old and in the cranial mesenteric artery (two to 79) in 10 horses from 239 days to 23 years old. Strongylus edentatus were in the large intestine (two to 101) of 12 horses, ranging in age from 2.5 to 23 years old and in the ventral abdominal wall (one to 53) of six horses from 239 days to 21 years old. Specimens (seven to 872) of Anoplocephala perfoliata were in all horses. Oxyuris equi (one to 129) were recovered from seven horses (330 days to 23 years old). Thelazia lacrymalis (one to 85) infected the eyes of five horses (317 days to 11 years old).

The effect of single and concomitant pathogen infections on condition and fecundity of the wild rabbit (Oryctolagus cuniculus).

We assessed the effect of two pathogens (myxoma virus and Eimeria stiedae) and five macroparasites (gastrointestinal helminth species) of the wild rabbit (Oryctolagus cuniculus) upon total host body mass and abdominal fat level. Additionally, we assessed the effects of these organisms on the number of foetuses in adult females during the peak breeding period. Both mass of abdominal fat and total body mass of the rabbit were negatively associated with myxoma virus infection and increasing helminth species richness. Total body mass was also negatively associated with the protozoan parasite E. steidae. No relationship was found between any of the parasites/pathogens and the number of foetuses in adult females, although only relatively small sample sizes were available for this section of the analysis. Increasing host body mass was positively associated with number of foetuses and we propose that mass reduction caused by the pathogen and parasite species could also have the consequence of reducing foetal number.