Natural Helminth Infections Research Articles

Modulation of the intestinal mucosal and cell-mediated response against natural helminth infection in the African catfish Clarias gariepinus

Fish gut is a versatile organ serving as the primary pathway for invasion by pathogens, particularly parasites, playing a crucial role in modulating the intestinal adaptive immune response. This study aimed to investigate the cellular-mediated reaction, mucosal acidity, and the expression of proliferating cell nuclear antigen (PCNA), vascular endothelial growth factor (VEGF), and CD68 in the intestines of catfish, Clarias gariepinus, naturally infected with helminths. Forty catfish were collected from the Nile River and examined for intestinal parasites. The intestinal tissues of the control and infected fish were fixed for histochemical and immunohistochemical studies. Two groups of helminths were found: cestodes Tetracampos ciliotheca and Polyonchobothrium clarias, and nematodes Paracamallanus cyathopharynx, with a prevalence rate of 63.63%, 18.0%, and 18.0%, respectively. Our results showed that the infected fish had a statistically significant rise in the activity of immune cells, including mast cells, eosinophil granular cells, and dendritic cells. This correlated with upregulation in the expressions of PCNA, VEGF, and CD68. Histochemical analyses demonstrated a marked increase in acidic mucus production, Sudan black B, and bromophenol mercury blue. This study enriches our understanding of the evolution of vertebrate immunity in combating intestinal parasitic infections and the host’s adaptive responses.

Formalin-fixed stool improves the performance of the Kato-Katz method.

Parasitic infections are a public health problem worldwide, including in Thailand. An epidemiological survey for helminthiasis based on stool examination uses the Kato-Katz method as recommended by the World Health Organization. Limitations of this method include the need for fresh stool, time requirement, and lack of quality control. The aim of this study was to enhance the efficiency of the Kato-Katz technique using formalin and glycerol solutions and to implement specimen preparation in fieldwork. For the Kato-Katz method, stool samples were divided into formalin-fixed and unfixed groups at various time points and processes. Fresh echinostome eggs were added to each stool group. Incubation with glycerol increased the clearing process. Each group was observed and photographed using a light microscope. Parasite eggs were imaged and compared using the standard Kato-Katz method. Visualization of echinostome eggs from formalin-fixed stool slides was significantly better than that from unfixed stool slides (p < 0.01). Stool samples fixed for 7 days retained normal echinostome eggs morphology. Incubation with glycerol for 1 h resulted in increased Kato-Katz performance by digesting the stool content and enhancing egg observation. Moreover, the results of the Kato-Katz method using fixed and fixed stool plus glycerol for natural helminth infection showed good quality of Opisthorchis viverrini and Taenia egg visualization and normal morphology with a clear background of slides. Formalin-fixed stool could be more suitable than fresh stool for the Kato-Katz method.

Post-weaning fecal egg count estimated breeding value is associated with greater antibody production after clostridial vaccination in Katahdin lambs

Previous work demonstrated that, Katahdin lamb survivability to weaning was affected by post-weaning fecal egg count (PFEC) estimated breeding values (EBV) and favored Low-PFEC lambs. Therefore, selection for PFEC is hypothesized to improve generalized immunity beyond resistance to parasitic infection. This study aimed to compare the effect of PFEC EBV on antibody production of Katahdin lambs in response to Clostridium perfringens type C&D and tetanus toxoid (CD&T) and C. perfringens type A vaccination. Lambs were grouped by their PFEC value into Low-PFEC (PFEC less than −50), Mid-PFEC (PFEC between −50 and +50), and High-PFEC (PFEC greater than +50). Prior to weaning and continuing 5 weeks after weaning, lambs were exposed to natural helminth infection on pasture and fecal samples were collected bi-weekly. Lamb FEC corresponded to genotype (950 epg High-PFEC vs. 452 epg Low-PFEC; P = <0.0001) over the course of the experiment. Three weeks prior to weaning lambs were vaccinated for CD&T and C. perfringens type A and again four weeks later. Serum samples were taken weekly for 8 weeks. Averaged across time, there was a stepwise decrease in immunoglobin (IgG) from Low-PFEC to High-PFEC groups (905 µg/mL, 739 µg/mL, and 644 µg/mL respectively; P < 0.0001). Upon booster vaccination IgG response was higher in Low-PFEC and Mid-PFEC groups than the High-PFEC group (2246 µg/mL, 2103 µg/mL vs. 1431 µg/mL, P < 0.0001). A moderate negative correlation was found between average serum IgG and lamb PFEC EBV (r = −0.55, P < 0.0001). Interestingly when PFEC values are less than − 50 or greater than + 50 lambs produce high or low IgG respectively. Collectively these data indicate that parasite resistant Katahdin lambs generate greater antibody response to clostridial vaccination.

123 Selection for Post-weaning Fecal Egg Count Estimated Breeding Value Is Associated with Greater Antibody Production After Clostridial Vaccination in Katahdin Sheep

Abstract In a previous study, Katahdin lamb survivability to weaning was affected by sire post-weaning fecal egg count estimated breeding values (PFEC EBV) where lambs sired by low PFEC rams had greater survivability than high-PFEC-sired lambs. Therefore, selection for PFEC may also select for improved generalized immunity. The aim of this study was to compare effects of divergent PFEC mating on antibody production in purebred Katahdin lambs in response to vaccination. Katahdin dams with a PFEC value of greater than zero were bred to positive (high-PFEC) FECEBV rams, likewise, dams with a PFEC value of less than zero were bred to negative (low-PFEC) FECEBV rams. All lambs were managed as one cohort until approximately 105 days of age. During this time on pasture, a natural helminth infection was established, blood samples were taken weekly, and fecal samples were collected bi-weekly. Lamb FEC corresponded to sire/dam genotype (943 epg high-PFEC vs. 455 epg low-PFEC; P &amp;lt; 0.001). Serum samples were taken weekly for 3 wks after initial vaccination for Clostridium perfringens type C&amp;D and C. perfringens type A and for 4 wks after booster vaccination, which occurred 3 wk following primary vaccination. Total circulating IgG was measured used an ovine-specific enzyme-linked immunosorbent assay (ELISA). To evaluate lamb IgG differences, data were analyzed using the General Linear Model (GLM) procedure of SAS with fixed effects of genotype, time, and genotype X time interactions. Means comparisons were performed on LS means of fixed affects or interactions, using Bonferroni adjustment. A genotype by time interaction revealed that IgG response to boostering favored LoPFEC lambs (1679.91 vs 1153.08 ug/mL, respectively; P &amp;lt; 0.001). When averaged across time, LoPFEC lambs generated greater IgG concentration than HiPFEC lambs (886.79 ug/mL vs 465.15 ug/mL, respectively; P &amp;lt; 0.001). These data indicate that PFEC breeding values in Katahdin sheep may predict immunological fitness outside the context of parasitic infections and has implications for use in selection of individuals less prone to disease.

Mycobacterium-Induced Th1, Helminths-Induced Th2 Cells and the Potential Vaccine Candidates for Allergic Asthma: Imitation of Natural Infection.

Bronchial asthma is one of the most chronic pulmonary diseases and major public health problems. In general, asthma prevails in developed countries than developing countries, and its prevalence is increasing in the latter. For instance, the hygiene hypothesis demonstrated that this phenomenon resulted from higher household hygienic standards that decreased the chances of infections, which would subsequently increase the occurrence of allergy. In this review, we attempted to integrate our knowledge with the hygiene hypothesis into beneficial preventive approaches for allergic asthma. Therefore, we highlighted the studies that investigated the correlation between allergic asthma and the two different types of infections that induce the two major antagonizing arms of T cells. This elucidation reflects the association between various types of natural infections and the immune system, which is predicted to support the main objective of the current research on investigating of the benefits of natural infections, regardless their immune pathways for the prevention of allergic asthma. We demonstrated that natural infection with Mycobacterium tuberculosis (Mtb) prevents the development of allergic asthma, thus Bacille Calmette-Guérin (BCG) vaccine is suggested at early age to mediate the same prevention particularly with increasing its efficiency through genetic engineering-based modifications. Likewise, natural helminth infections might inhabit the allergic asthma development. Therefore, helminth-derived proteins at early age are good candidates for designing vaccines for allergic asthma and it requires further investigation. Finally, we recommend imitation of natural infections as a general strategy for preventing allergic asthma that increased dramatically over the past decades.

Helminth infection induces non-functional sensitization to house dust mites.

BackgroundIgE characterizes the humoral response of allergic sensitization but less is known about what modulates its function and why some patients present clinical symptoms for a given IgE level and others do not. An IgE response also occurs during helminth diseases, independently of allergic symptoms. This response could be a model of non-functional IgE.ObjectiveTo study the IgE response against environmental allergens induced during natural helminth infection.MethodsIn 28 non allergic subjects from the periphery of Ho Chi Minh city with (H+, n = 18) and without helminth infection (H-, n = 10), we measured IgE and IgG4 against several components of Dermatophagoïdes pteronyssinus (Dpt) and Ascaris (a marker of immunization against nematodes), and determined the IgE component sensitization profile using microarray ISAC biochips. The functional ability of IgE to induce degranulation of cultured mast cells was evaluated in the presence of Dpt.ResultsNon allergic H+ subjects exhibited higher levels of IgE against Dpt compared to H- subjects. Dpt IgE were not functional in vitro and did not recognize usual Dpt major allergens. IgE recognized other component allergens that belong to different protein families, and most were glycosylated. Depletion of IgE recognizing carbohydrate cross-reactive determinant (CCD) did not induce a reduction in Dpt IgE. The Dpt IgG4 were not significantly different.ConclusionHelminth infections induced IgE against allergens such as Dpt and molecular components that belong to different sources as well as against CCD (such as β-1,2-xylose and/or ⍺-1,3-fucose substituted N-glycans). Dpt IgE were not able to induce degranulation of mast cells and were not explained by sensitization to usual major allergens or N-glycans.

Anthelmintic drugs modulate the acute phase immune response but not the microbiota in wild Song Sparrows

Abstract Co-infection with microparasites (e.g., bacteria) and macroparasites (e.g., helminths) is often the natural state for wild animals. Despite evidence that gut helminths can bias immune responses away from inflammatory processes, few field studies have examined the role that helminths, or their potential interactions with internal microbial communities, play in modulating immunity in free-living, wild birds. Here, we used anthelmintic drugs to treat wild Song Sparrows (Melospiza melodia) for helminth infections and measured markers of systemic inflammation (heterothermia and locomotor activity) in response to an immune challenge with lipopolysaccharide (LPS), a cell wall component of gram-negative bacteria. Using birds from a population that previously showed high helminth prevalence, we monitored skin temperature and activity remotely using automated radio telemetry. We also collected cloacal swabs to determine whether drug treatment was associated with changes in the cloacal microbiota, and whether cloacal microbial community structure was associated with the severity of birds’ immune responses. Because helminths can reduce the severity of inflammatory immune responses in other species, we predicted that in comparison with untreated control birds, anthelmintic-treated birds would be more lethargic and display higher fevers when challenged with LPS. Consistent with these predictions, anthelmintic-treated birds expressed higher fevers in response to immune challenge. However, all LPS-challenged birds decreased locomotor activity to a similar degree, regardless of anthelmintic treatment. Although several individual indicator bacterial taxa were strongly associated with anthelmintic treatment, this treatment did not alter overall bacterial alpha- and beta- diversity. Similarly, we did not find evidence that bacterial community diversity influenced the severity of immune responses to LPS. These results suggest that under field conditions, natural helminth infection can reduce the severity of songbirds’ thermoregulatory responses (fever) during an immune challenge, without major impacts on internal microbial communities or behavioral responses to infection.

GAS6 signaling tempers Th17 development in patients with multiple sclerosis and helminth infection.

Multiple sclerosis (MS) is a highly disabling neurodegenerative autoimmune condition in which an unbalanced immune response plays a critical role. Although the mechanisms remain poorly defined, helminth infections are known to modulate the severity and progression of chronic inflammatory diseases. The tyrosine kinase receptors TYRO3, AXL, and MERTK (TAM) have been described as inhibitors of the immune response in various inflammatory settings. We show here that patients with concurrent natural helminth infections and MS condition (HIMS) had an increased expression of the negative regulatory TAM receptors in antigen-presenting cells and their agonist GAS6 in circulating CD11bhigh and CD4+ T cells compared to patients with only MS. The Th17 subset was reduced in patients with HIMS with a subsequent downregulation of its pathogenic genetic program. Moreover, these CD4+ T cells promoted lower levels of the co-stimulatory molecules CD80, CD86, and CD40 on dendritic cells compared with CD4+ T cells from patients with MS, an effect that was GAS6-dependent. IL-10+ cells from patients with HIMS showed higher GAS6 expression levels than Th17 cells, and inhibition of phosphatidylserine/GAS6 binding led to an expansion of Th17 effector genes. The addition of GAS6 on activated CD4+ T cells from patients with MS restrains the Th17 gene expression signature. This cohort of patients with HIMS unravels a promising regulatory mechanism to dampen the Th17 inflammatory response in autoimmunity.

Hydrolytic bacteria associated with natural helminth infection in the midgut of Red Sea marbled spinefoot rabbit fish Siganus rivulatus

Fish infected with intestinal helminths or pathogenic bacteria can pose a serious risk of foodborne disease, threatening human and animal health, and require high attention. The current study investigates the diversity and composition of the microbiota in the midgut of rabbit fish Siganus rivulatus naturally infected with helminths. Six species of helminth parasites, including the digeneans Hexangium sigani and Gyliauchen volubilis, the acanthocephalans Sclerocollum rubrimaris and Neorhadinorhynchus macrospinosus, and the nematodes Procammalanus elatensis, and Ascaridoid larvae were recorded in the fish intestine. P. elatensis had the highest prevalence, occurring in 65% of infected fish; 72.2% of infected fish had concurrent infection with two or more helminth species. The total count of aerobic bacteria ranged from 1 to 305 colony-forming units (CFU)/g midgut contents. Four hydrolytic bacteria were recovered from the infected samples: Escherichia coli (ASU 31), Bacillus cereus (ASU 36) MN955553, Bacillus thuringiensis (ASU 34) MN955550, and Novosphingobium aromaticivorans (ASU 35) MN955552, which were identified using 16S rRNA genes. Bacterial richness was significantly correlated with concurrent parasitic infection and high content of extracellular hydrolytic amylases, proteases, cellulases, and lipases. The present results showed that the composition of the microbiota was affected by natural helminth infections in Siganus rivulatus, and the significant interaction between parasitic load and intestinal pathogenic bacteria, which may be primary in fish diseases etiology.

Immunogenicity and protection induced by recombinant Toxocara canis proteins in a murine model of toxocariasis

Toxocariasis, a natural helminth infection of dogs and cats caused by Toxocara canis and T. cati, respectively, that are transmitted to mammals, including humans. Infection control is based currently on periodic antihelmintic treatment and there is a need for the development of vaccines to prevent this infection. Materials and Methods: Eight potential vaccine candidate T. canis recombinant proteins were identified by in silico (rTcGPRs, rTcCad, rTcVcan, rTcCyst) and larval proteomics (rTES26, rTES32, rMUC-3 and rCTL-4) analyses. Immunogenicity and protection against infectious challenge for seven of these antigens were determined in a murine model of toxocariasis. C57BL/6 female mice were immunized with each of or combinations of recombinant antigens prior to challenge with 500 T. canis embryonated eggs. Levels of specific antibodies (IgG, IgG1, IgG2a and IgE) in sera and cytokines (IL-5, INF-ɣ and IL-10) produced by antigens-stimulated splenocytes, were measured. Presence of specific antibodies to the molecules was measured in sera of T. canis-seropositive dogs and humans. Results: All seven molecules were immunogenic in immunized mice; all stimulated significantly elevated levels of specific IgG, IgG1 or IgG2a and six were associated with elevated levels of specific IgE; all induced elevated production of IFN- ɣ and IL-10 by splenocytes, but only the in silico-identified membrane-associated recombinants (rTcCad, rTcVcan, and rTcCyst) induced significantly increased IL-5 production. Vaccination with two of the latter (rTcCad and rTcVcan) reduced larval loads in the T. canis challenged mice by 54.3% and 53.9% (P < 0.0001), respectively, compared to unimmunized controls. All seven recombinants were recognized by T. canis-seropositive dog and human sera. Conclusion: The identification of vaccine targets by in silico analysis was an effective strategy to identify immunogenic T. canis proteins capable of reducing larval burdens following challenge with the parasite. Two recombinant proteins, rTcCad and rTcVcan, were identified as promising vaccine candidates for canine toxocariasis.

Generalized urticaria induced by the Na-ASP-2 hookworm vaccine: Implications for the development of vaccines against helminths

Necator americanus Ancylostoma-secreted protein 2 (Na-ASP-2) is secreted by infective hookworm larvae on entry into human hosts. Vaccination of laboratory animals with recombinant Na-ASP-2 provides significant protection against challenge infections. In endemic areas antibodies to Na-ASP-2 are associated with reduced risk of heavy N americanus infections. To assess the safety and immunogenicity of recombinant Na-ASP-2 adjuvanted with Alhydrogel in healthy Brazilian adults previously infected with N americanus. Participants were randomized to receive Na-ASP-2 or hepatitis B vaccine. Major IgG and IgE epitopes of the Na-ASP-2 molecule were mapped by using sera from these same subjects. Seroepidemiologic studies in adults and children residing in hookworm-endemic areas were conducted to assess the prevalence of IgE responses to Na-ASP-2. Vaccination with a single dose of Na-ASP-2 resulted in generalized urticarial reactions in several volunteers. These reactions were associated with pre-existing Na-ASP-2-specific IgE likely induced by previous hookworm infection. Surveys revealed that a significant proportion of the population in hookworm-endemic areas had increased levels of IgE to Na-ASP-2. Epitope mapping demonstrated sites on the Na-ASP-2 molecule that are uniquely or jointly recognized by IgG and IgE antibodies. Infection with N americanus induces increased levels of total and specific IgE to Na-ASP-2 that result in generalized urticaria on vaccination with recombinant Na-ASP-2. These data advance knowledge of vaccine development for helminths given their propensity to induce strong T(H)2 responses. Study data highlight the important differences between the immune responses to natural helminth infection and to vaccination with a recombinant helminth antigen.

Genetic resistance to natural helminth infections in two chicken layer lines

Groups of Lohmann Brown (LB) and Lohmann Selected Leghorn (LSL) hens were reared under helminth-free conditions and kept afterwards together in a free range system. Mortality rate, body weight development, laying performance and faecal egg counts (FEC) were recorded during a 12 month laying period. At the end of the laying period, 246 LSL and 197 LB hens were necropsied and worms counted following the World Association for the Advancement of Veterinary Parasitology (W.A.A.V.P.) guidelines. In addition adult Heterakis gallinarum and Ascaridia galli were sexed and measured for length.Significant (P<0.01) differences were observed in mortality rates between LSL and LB animals (12.9 vs. 5.7%). LSL hens showed significantly (P<0.05) higher FEC when compared with LB hens at almost all dates of monitoring. Almost all animals became infected with at least one helminth species. The most prevalent species were H. gallinarum, Capillaria spp. and A. galli. LB hens showed a significantly (P<0.05) higher average number of adult H. gallinarum, Capillaria spp. and tapeworms when compared with LSL animals. However, number of adult A. galli was in tendency lower in these animals. In total, LB had a significantly (P<0.05) higher worm burden than LSL (192.3 vs. 94.3). The estimated heritabilities for total worm burden were 0.23 (SE±0.12) in LSL and 0.75 (SE±0.21) in LB, respectively. The number of all different helminth species were positively correlated.The sex ratio of H. gallinarum and A. galli and the average worm lengths were not significantly (P>0.05) different between the genotypes.There was no significant phenotypic correlation between body weight and worm burden in LSL, whereas it was the case in LB (r=0.17, P<0.05).Based on the estimated heritabilities it is possible to select for helminth resistance in both genotypes.

Influence of protein supplementation on the resistance and resilience on young hair sheep naturally infected with gastrointestinal nematodes during rainy and dry seasons

Thirty, 4-month-old entire Santa Ines lambs were grazed on an Andropogon gayanus pasture, during a 34-week period (rainy season weeks 0–20 and dry season weeks 21–34) and allocated in two treatment groups ( n = 15) each with different protein supplementation: high protein (HP—19% CP) and low protein (LP—11% CP). These were subdivided into those receiving anthelmintic treatment (c) ( n = 7) and without anthelmintic treatment (i) ( n = 8). The objective was to evaluate the effects of supplementation with protein on resistance and resilience to natural helminth infection of hair breed lambs. Lamb weight, blood collection and faecal egg counts (FEC) were carried out monthly. The lambs were slaughtered after 34 weeks, when worm burdens, worm length and eosinophil cell counts were taken. The sheep on treatments HPc and HPi were heavier in live weight than those from LPi and LPc ( P < 0.05) at the end of the rainy period. The HPc group finished heavier ( P < 0.05) than the other groups in the dry season, which had no significant differences between them. The predominant species of nematode found was T. colubriformis followed by H. contortus, Trichuris globulosa and Moniezia expansa. Animals on HPi had lower FEC than LPi ( P < 0.05). The number of worms was lower for both HP groups ( P < 0.05) with worm length shorter in the HPc group ( P < 0.05) compared with all other groups. The number of eosinophils was higher in animals in the LPi group, which also showed anaemia and lower plasma urea at the end of the dry season. Diet supplementation with high protein was able to improve resilience and resistance to natural infection by endoparasites during the rainy season. In the dry season there was a decrease in both of these traits, which were intimately linked to the quality of available forage under tropical conditions.

First report of a natural helminth infection in the Japanese quail Coturnix japonica Temminck &amp; Schlegel (Aves, Phasianidae, Galliformes) in the neotropical region

The present findings are related to the report of the first natural helminth infection in the Japanese quail, Coturnix japonica Temminck &amp; Schlegel, 1849 in Brazil. The kidney trematode Tanaisia inopina Freitas, 1951 is referred for the first time in the investigated host.

Primeiro relato de infecção helmíntica natural na codorna-doméstica Coturnix japonica Temminck & Schlegel (Aves, Phasianidae, Galliformes) na região Neotropical.

The present findings are related to the report of the first natural helminth infection in the Japanese quail, Coturnix japonica Temminck & Schlegel, 1849 in Brazil. The kidney trematode Tanaisia inopina Freitas, 1951 is referred for the first time in the investigated host.

The impact of natural helminth infections and supplementary protein on growth performance of free-range chickens on smallholder farms in El Sauce, Nicaragua

Three on-farm studies were conducted in Nicaragua during three consecutive years (1999–2001) to assess the impact of natural helminth infections on growth performance of free-range chickens aged 3–4 months. On all participating farms, half of the chickens were treated regularly with anthelmintics (Trifén avícola – a combined formulation of piperazine, phenothiazine and dichlorophen – or albendazole) to express the growth potential of non-infected birds, whereas the other half served as non-treated controls. In 1999, treated chickens had a 39% higher weight gain compared to the control group 6 weeks after the first treatment on 15 farms. In 2000 and 2001, treated chickens had similar weight gain as the control group 10 weeks after the first treatment on 7 farms and 12 farms, respectively. The main reason for the very-different weight gain figures seems to be the weather conditions. In 1999, the study site experienced a rainy season with precipitation far above average, whereas in 2000 and 2001 the rainy seasons had precipitations far below average. Based on these findings, routine use of anthelmintics in the study area would only be recommended in wet years when production losses due to helminth infections seem to be pronounced. In 2001, the study set-up included an assessment of the effect of protein supplementation (soybean) on growth on six farms. Supplemented chickens (treated and non-treated with anthelmintics) had 17% higher weight gain than non-supplemented. Protein supplementation affected neither worm burdens nor faecal egg counts for any of the studied helminths. The post-mortem examinations showed that Trifén reduced burdens of Ascaridia galli, Heterakis gallinarum, and cestodes (efficacies of 100, 100 and 67%, respectively). Albendazole reduced burdens of H. gallinarum (efficacy of 100%). Efficacies against other helminths were difficult to assess due to low worm burdens. Chickens treated with albendazole had lower Ascaridia and Heterakis faecal egg counts than non-treated chickens.

Effects of gastrointestinal helminth infections and plane of nutrition on the health and productivity of F1 (West African Dwarf × Sahelian) goat crosses in The Gambia

A two by two factorial design including natural helminth infections (dewormed ‘D’ or not dewormed ‘ND’) and different levels of diet (basal ‘B’ or basal diet plus supplement ‘S’) was used to assess the effect of helminth infections and plane of nutrition on health and productivity of F1 (West African Dwarf (WAD) × Sahelian) crosses. The pasture composed the basal diet and supplemented animals received cottonseed and rice bran. Feed composition analysis revealed that the pasture did not provide sufficient nutrients for reproduction requirements. Feed supplementation had a significant effect on weight gain of does during pregnancy and lactation, and milk off-take was significantly higher in supplemented does compared to non-supplemented ones (31.3±2.5 l versus 17.7±2.5 l respectively, P<0.01). A peri-parturient rise in strongyle egg output was noted, and diet supplementation tended to reduce faecal egg count and to increase packed cell volume (PCV), mainly during the dry season. Deworming had a significant effect on red blood cell (RBC) count, PCV and haemoglobin (Hb) concentration, mainly during the period of peak strongyle egg output (season × deworming: P<0.001 for RBC and PCV and P<0.05 for Hb). Helminth infections combined with a basal diet seriously affected weight gain but the interaction of deworming and diet was not significant. In groups receiving the basal diet, dewormed animals had a significantly higher milk yield than those that were not dewormed (23.5±3.3 l versus 12.0±3.7 l, respectively; interaction diet × deworming: P<0.05). The higher daily weight gains of offspring born from dewormed does might be explained by the fact that, in addition to the effect of deworming on milk yield in animals receiving basal diet, the kids were less exposed to helminth eggs, whereas does that were not dewormed constituted a greater source of helminth infection for their kids.

Susceptibility of trypanotolerant West African Dwarf goats and F1 crosses with the susceptible Sahelian breed to experimental Trypanosoma congolense infection and interactions with helminth infections and different levels of diet

Forty pure West African Dwarf (WAD) goats and 35 of its F1 crosses with the Sahelian breed were used in a multifactorial experimental design to evaluate the effects of an experimental Trypanosoma congolense infection and interactions with natural helminth infections and different levels of diet on health and productivity of these two breeds. Trypanosome infection caused a severe drop in packed cell volume (PCV), but this was not significantly affected by breed. Neither deworming nor diet had any effect on the course of anaemia after trypanosome infection. The mean score of parasitaemia tended to be higher in crossbreeds than in WAD goats although this was not significant ( P>0.05). Similarly, the antibody response to trypanosome infection was not significantly different between breeds. Parasitaemia level was significantly influenced by the level of diet with the group under high supplementation having a higher mean parasitaemia score than the group under low supplementation. Weight loss due to trypanosome infection tended to be greater in crossbreeds than in WAD goats ( P>0.05). During this study, there was no difference in mean helminth egg output between crossbred and WAD goats. However, between weeks 4 and 10 after trypanosome infection (corresponding to a period of heavy rainfall and highly infective pastures), the mean egg output was higher in the crossbreeds. The immunosuppressive effect of trypanosome infections was revealed by a lower antibody response to Haemonchus contortus in infected animals compared to the uninfected controls. Trypanosome infection tended to increase strongyle egg output. This study did no reveal any superior trypanotolerance of WAD goats compared to crossbreeds.

Summer-arrested development of abomasal trichostrongylids in Awassi sheep in semi-arid areas of North-West Syria

Inhibition in trichostrongylids was studied in Awassi sheep in North-west Syria, which has cold winters and hot summers. On six occasions during a 1-year period, five ewes with natural helminth infections were slaughtered after being held in pens for 3 weeks. The percentage of inhibited larvae was lowest in January (6%); it increased during the spring to 76.7% in April and to 84.6% in June and then decreased during the autumn (57.1% in September, 26.1% in December). Inhibition occurred mainly during the early fourth stage in mucosa but was also observed during the late fourth stage in digesta. Teladorsagia circumcincta was the main species involved, but it seemed that this phenomenon also occurred in Marshallagia marshalli.

Concinnum epomopis Sandground, 1937 (Dicrocoeliidae) from the pancreas of the West African fruit batEidolon helvum in Nigeria

The natural arthropod and helminth infections of a vast colony of a West African fruit batEidolon helvum were studied over a period of 2 years. The seasonal prevalence of a non-specific ectoparasiteCyclopodia greeffi Karsch, 1884 is presented, while the complete absence of endoparasitic infection in the gut is noted. A single helminth infection withConcinnum epomopis Sandground, 1937 (Digenea) in the pancreas was found. This digenean is redescribed and data on the occurrence is presented. Helminth infection as a means of population control of the fruit bat is ruled out, as infections appeared to be accidental; the factors determining the prevalence and frequency of infections are considered. The significant factors responsible for the general overall poor helminth fauna of fruit bats in comparison to the generally diverse helminth fauna of the local insectivorous bats are discussed. Histopathological changes resulting from infection are recorded.