Effects of lactation on Trichostrongylus colubriformis infections in the guinea pig

Effects of lactation on Trichostrongylus colubriformis infections in the guinea pig. International journal for Parasitology, 4: 177–181. An increase in parasite egg output occurred in lactating guinea pigs infected with Trichostrongylus colubriformis, compared with that of either non-lactating or nulliparous females similarly infected. The lactating animals carried more parasites than either of the other two groups both as fourth stage larvae 9 days after infection and as adults at the peak of egg output 19 days after infection. Both the nulliparous and the non-lactating female guinea pigs had more mast cells and eosinophils in the small intestinal mucosa than did the lactating females.The behaviour of T. colubriformis in the lactating guinea pig is considered to be substantially the same as that of the various nematodes which have been studied in the lactating ewe.     

Expression of genes in gastrointestinal and lymphatic tissues during parasite infection in sheep genetically resistant or susceptible to Trichostrongylus colubriformis and Haemonchus contortus

Resistance to an acute gastrointestinal nematode (GIN) infection is dependent on the ability of the host to recognise the parasite and mount a protective Th2 response. It is hypothesised that lambs which are genetically susceptible to GIN will differentially up-regulate Th1-type genes and therefore remain susceptible to chronic parasitism compared with genetically resistant lambs which will differentially up-regulate Th2-type genes and clear the parasite infection. Two selection flocks, in which lines of Merino sheep produced lambs genetically resistant or susceptible to GIN, were acutely challenged once or thrice with either Haemonchus contortus or Trichostrongylus colubriformis. Faecal-egg counts (FECs), and plasma and tissue anti-parasite (H. contortus or T. colubriformis) antibody isotype responses showed that resistant animals challenged three times with T. colubriformis established a protective Th2 response (negligible FEC, IgG1 and IgE) whereas susceptible animals required multiple challenges to establish a significant IgG1 response despite FECs remaining high. Trichostrongylus colubriformis elicited a more pronounced host response than H. contortus. RNA extracted from tissues at the site of each parasite infection and associated lymph nodes were interrogated by microarray and quantitative PCR analyses to correlate host gene expression to FECs and antibody responses. The IFN-γ inducible gene cxcl10 was up-regulated in the susceptible line of the Trichostrongylus selection flock sheep after a tertiary challenge with the parasites H. contortus and T. colubriformis. However, a uniform pattern of genes was not up-regulated in resistant animals from both selection flocks during both parasite infections, suggesting that the mode of host resistance to these parasites is different, although some similarities in host susceptibility were apparent.     

The response of the regional lymph node of guinea-pigs to primary and challenge infection with the nematode, Trichostrongylus colubriformis

Responses characteristic of both cell-mediated immunity and the production of humoral antibodies occurred in the regional lymph node (mesenteric) of guinea-pigs following primary and challenge infection with the nematode Trichostrongylus colubriformis. In addition, depletion of lymphocytes in the paracortical areas and pronounced infiltration with basophil and eosinophil leucocytes were observed. All these changes were chronologically related to parasite rejection.     

The response of lambs to vaccination at weaning with irradiated Trichostrongylus colubriformis larvae: segregation into 'responders' and 'non-responders'

Dineen J. K., Gregg P. and Lascelles A. K. 1978. The response of lambs to vaccination at weaning with irradiated Trichostrongylus colubriformis larvae: segregation into ‘responders’ and ‘non-responders’. International Journal for Parasitology8: 59–63. Groups of colostrum fed and colostrum deprived lambs were vaccinated with irradiated Trichostrongylus colubriformis larvae at weaning (3 months) and challenged with normal infective larvae. As there was no significant difference between the worm counts of these groups after challenge, it was concluded that the failure of lambs, generally, to respond to vaccination as vigorously as mature sheep, was not due to ‘feed-back inhibition’ of the immune response by the action of maternal antibody.However the results showed that the lambs segregated into ‘responders’ and ‘non-responders’. The mean worm count of responders was 1560 whereas for non-responders this was 24,340. A responder was defined as an animal whose worm count was less than the lower limit of the 99 % confidence interval of unvaccinated controls. These results suggest that genetically-determined factors play an important role in the responsiveness of lambs to vaccination.Whereas counts of globule leucocytes in duodenal tissues were negatively correlated with worm counts (i.e. positively correlated with resistance), counts of both eosinophils and neutrophils were positively correlated with worm counts. These findings suggest that either globule leucocytes are involved in the resistance mechanism, or they are by-products of cellular events involved in resistance. On the other hand it is unlikely that either eosinophils or neutrophils are involved in the mechanism of resistance.     

The effect of sire selection on the response of lambs to vaccination with irradiated Trichostrongylus colubriformis larvae

Dineen, J. K. and Windon, R. G. (1980). The effect of sire selection on the response of lambs to vaccination with irradiated Trichostrongylus colubriformis larvae. International Journal for Parasitology10: 189–196. Rams selected for responsiveness and unresponsiveness to vaccination with irradiated T. colubriformis larvae at an early age were mated to unselected random bred ewes. Progeny were vaccinated with 20,000 irradiated larvae at 8 and 12 weeks of age, given anthelmintic treatment at 16 weeks and challenged with 20,000 normai larvae at 17 weeks. The results, based on wether worm counts and ewe faecal egg counts, showed significant differences between responder and non-responder progeny. There was a significant correlation between worm counts and faecal egg counts of half-sibs from the same sire group. The occurrence of globule leucocytes was inversely related to worm burdens of wether progeny, however, no clear relationship was found with eosinophils. In vitro lymphocyte stimulation using T. colubriformis L₃ antigen, concanavalin A and lipopolysaccharide showed that statistically defined responder progeny, pooled from both responder and non-responder sire groups, gave higher responses than non-responder lambs after vaccination. The results confirm that genetically-determined factors are involved in the response of lambs to vaccination at an early age, and indicate that rapid genetic progress may be achieved in the type of mating usually carried out under fleld conditions.     

Studies on the kinetics of expulsion by guinea-pigs of primary infections with the intestinal nematode parasite Trichostrongylus colubriformis

Heston strain guinea-pigs were infected with 1000 Trichostrongylus colubriformis infective larvae and the kinetics of parasite expulsion from the host studied. Expulsion began approximately 15 days after infection, after which log worm count declined from an initial level of approximately 2·77 at a rate of approximately 0·1 per day. There was no significant difference in worm counts in each sex.     

Investigations of 'transfer factor' activity in immunity to Ostertagia circumcincta and Trichostrongylus colubriformis infections in sheep.

Immunity was successfully transferred by ‘Transfer Factor’ prepared from leucocytes of two adult Scottish Blackface donor rams infected with O. circumcincta and T. colubriformis to 4-month-old susceptible Fin X Dorset lambs. The immunity was expressed by a significantly reduced faecal egg count and worm burden compared to challenged, untreated controls. The immunity was comparable to that produced in another group of lambs given an initial infection prior to challenge with both parasites.     

Immunity against trichostrongylus colubriformis infection in guinea-pigs and sheep: Some comparisons with Nippostrongylus brasiliensis infection in the rat

In Nippostrongylus brasiliensis infection in rats there is evidence that antibodies ‘damage’ the worms rendering them susceptible to other components of the host immune response. Some of the experiments from which this evidence was obtained were repeated in Trichostrongylus colubri-formis infections in guinea-pigs and sheep.Lesions similar to those described in ‘damaged’ N. brasiliensis were present in T. colubriformis, but unlike damaged N. brasiliensis, damaged T. colubriformis were not rapidly expelled from the intestine of either normal or adoptively immunized hosts. Other differences between the two infections included the failure of serum from T. colubriformis-immune donors either to regularly transfer immunity against infection to non-immune recipients or to endow additional immunity on recipients of lymphoid cells from immune donors.It is suggested that the results might reflect differences between the manner in which guinea-pigs and rats achieve immune expulsion of gastro-intestinal nematode parasites.     

Vaccination against the nematode Trichostrongylus colubriformis. III. Some observations on factors influencing immunity to infection in vaccinated guinea-pigs

Rothwell T. L. W. 1978. Vaccination against the nematode Trichostrongylus colubriformis. III. Some observations on factors influencing immunity to infection in vaccinated guineapigs. International Journal for Parasitology8: 33–37. Guinea-pigs were protected against infection with T. colubriformis when soluble material extracted from fourth-stage larvae was administered by the subcutaneous, intradermal, intraperitoneal and intraduodenal but not oral routes. The level of immunity following vaccination by the various effective routes was similar. Mature animals were found to respond significantly better to vaccination than immature animals. Significant immunity was present 10 days after vaccination but higher levels were found after 20 and 40 days. A single dose of vaccine was as effective as three divided doses. Finally, it was found that the adjuvant aluminium hydroxide gel, but not B. pertussis vaccine or levamisole improved the level of immunity to infection which followed vaccination.     

Studies of the responses of basophil and eosinophil leucocytes and mast cells to the nematode Trichostrongylus colubriformis. Ultrastructural changes in basophils and eosinophils at the site of infection.

Basophil and eosinophil leucocytes infiltrate the small intestinal lamina propria of guinea-pigs infected with the nematode Trichostrongylus colubriformis. By comparing the morphology of both cell types at the site of infection with bone marrow and buffy coat cells, it was found that, after entering the lamina propria, basophils developed an electron lucent halo beneath the granule-limiting membrane while the characteristic orderly periodicity of the granules changed to a fibrillar or amorphous appearance. The granules also tended to coalesce but remained within the cell. Approximately half the eosinophils at the site of infection developed deficiencies in the amorphous outer matrix of their granules but showed no obvious change in the central electron-dense cores.     

Gastric dysfunction in sheep infected with Trichostrongylus colubriformis, a nematode inhabiting the small intestine

Barker I. K. and Titchen D. A. 1982. Gastric dysfunction in sheep infected with Trichostrongylus colubriformis, a nematode inhabiting the small intestine. International Journal for Parasitology12: 345–356. Six of 12 lambs infected with Trichostrongylus colubriformis had reduced abomasal acidification (pH 4.0–8.1) in comparison with uninfected pair-fed and replete controls (pH <3.5), though less than 0.8% of the worm burden was in the abomasum. Loss of prominence of parietal cells and encroachment of mucous cells deep into fundic glands was seen by light microscopy. Under the electron microscope, parietal cells had little canalicular or tubulovesicular development, had large vacuoles, many polyribosomes and few mitochondria in comparison with those in controls. In a further 8 sheep prepared with abomasal fistulae and separated fundic pouches and inoculated orally with T. colubriformis, the volume of fundic pouch secretion declined as feed intake dropped and in 7 out of 8 animals H⁺ concentration in fundic pouch secretion also fell. Infection generally reduced volume and acidity of pouch secretion more than did a pre-inoculation fast. In 5 sheep, abomasal content exceeded pH 4. Inoculation of T. colubriformis by enterotomy and Ostertagia circumcincta per os, in a lamb with a separated fundic pouch, caused depression of volume and acidity of pouch secretion characteristic of T. colubriformis infection, rather than the hypersecretion typical of abomasal infection with Ostertagia. Factors inhibitory to parietal cell differentiation and gastric acid secretion may be released from the small intestine of some sheep in response to changes in the gut induced by the presence of T. colubriformis. Abomasal dysfunction is a manifestation of severe intestinal trichostrongylosis.     

Uptake of thiabendazole and its effects on glucose uptake and carbohydrate levels in the thiabendazole-resistant and susceptible Trichostrongylus colubriformis

Sangster N. C. and Prichard R. K. 1984. Uptake of thiabenzadole and its effects on glucose uptake and carbohydrate levels in thiabendazole-resistant and susceptible Trichostrongylus colubriformis. International Journal for Parasitology14:121–126. Some possible mechanisms of thiabenzadole (TBZ) resistance have been investigated in Trichostrongylus colubriformis. Uptake of TBZ and 3-0-methyl glucose and changes in carbohydrate levels in a TBZ-resistant and a TBZ-susceptible strain of T. colubriformis were measured after in vitro incubation, in the absence or presence of TBZ. The rate of TBZ uptake in adult worms was greater in the resistant strain but the difference was not statistically significant. Final concentrations of TBZ in resistant worms were significantly greater than in the susceptible strain, but there was no difference in TBZ uptake by eggs of either strain. A mechanism of resistance based on decreased drug uptake by resistant parasites is thus unlikely. Resistant worms absorbed 3-0-methyl glucose faster than susceptible parasites, however, this rate was unchanged in either strain when the worms were exposed to TBZ and indicates that the drug does not affect glucose uptake. Levels of glucose, trehalose and glycogen fell during the incubation with the decrease being more pronounced in the resistant strain. When the worms were exposed to TBZ the same changes in carbohydrate levels occurred except for resistant worms maintained anaerobically where levels were higher, showing that TBZ does not affect the rate of carbohydrate utilization.     

IL-5 drives eosinophils from bone marrow to blood and tissues in a guinea-pig model of visceral larva migrans syndrome

This study was undertaken to evaluate the role of IL-5 in eosinophil migration and in the maintenance of eosinophilia in a guinea-pig model of visceral larva migrans syndrome. The results show that the infection of animals with Toxocara canis induced an early increase in serum IL-5 levels that might be essential for eosinophil differentiation and proliferation and for the development of eosinophilia. When infected guinea-pigs were treated with mAb anti-IL-5 (TRFK-5) given at the same time or 1 or 3 days after infection, there was a high percentage of reduction of eosinophil counts 18 days after infection. However, when the mAb was administered during the peak of eosinophilia, there was high inhibition in blood, no inhibition in bronchoalveolar lavage fluid (BALF) or peritoneum and an increase in eosinophil numbers in bone marrow. Thus, a basic level of IL-5 may be essential to drive eosinophils from bone marrow to blood and tissues, and for the maintenance of eosinophilia in infected animals. We may also conclude that when eosinophils have already migrated to the lungs, TRFK-5 has no power to inhibit eosinophilia, which is also under control of local lung cells producing IL-5. In this way, only one later TRFK-5 treatment may not be sufficient to modify the lung parenchyma microenvironment, since T. canis antigens had already stimulated some cell populations to produce IL-5.     

The effect of vaccinating infection during pregnancy and dietary protein supply on the peri-parturient immune response of sheep to infection with Teladorsagia circumcincta and Trichostrongylus colubriformis larvae

It is well established that dietary protein supply can influence the peri-parturient breakdown of immunity to nematode parasites but there is no information on the importance of exposure to nematode larvae during pregnancy for this response. We investigated this by exposing housed pregnant sheep, scanned as carrying two lambs, to a vaccinating infection with a trickle mixed infection of Teladorsagia circumcincta and Trichostrongylus colubriformis larvae (L3) or to no infection during weeks − 9 to − 4 relative to parturition. At the beginning of week − 3 all sheep were treated with anthelmintic to remove any vaccinating worm burden and from week − 2 to week +6 received a trickle challenge infection with the same nematodes. Within each vaccinating treatment there were two nutritional treatments (no. = 20 per subgroup) designed to provide 1.5 or 1.0 and 1.3 or 0.8 of metabolisable protein (MP) requirement during pregnancy and lactation, respectively. Five ewes were necropsied during weeks +1 and +3 to measure worm burdens and mucosal inflammatory cells and the remainder maintained until week +6. Serum levels of total, IgA and IgE antibodies against L3 antigen of each nematode were measured.Scanning errors and lamb losses resulted in some ewes carrying and/or rearing only one lamb. Numbers of lambs reared was therefore introduced as a treatment effect. Vaccinating infection delayed the peri-parturient rise in faecal egg count (FEC) by an average of 2 weeks but its effect on FEC during the first 6 weeks of lactation was smaller and less persistent than that of dietary MP supply and single- v. twin-suckling.Populations of both nematodes were lower in association with high MP supply, vaccination and single suckling. These changes were associated with increases in numbers of mucosal mast cells (MMC) as a result of both increased MP supply and vaccination. Evidence for a more rapid return of host ability to limit populations of the abdominal nematode T. circumcincta than of the intestinal nematode T. colubriformis was associated with fewer eosinophils and more globule leucocytes (GL) in abomasal than in intestinal tissue.None of the serum antibody isotypes was affected by dietary protein supply. Total and IgA antibodies were maintained by a current larval (vaccinating) intake. IgA titres, however, increased progressively during pregnancy, especially in twin-bearing ewes. IgE titres appeared to be sensitive primarily to the reproductive cycle itself, peaking around parturition.This work supports the conclusion that availability of MP supply influences the recruitment and activity of cells of the immune armoury of the gastro-intestinal tract to nematode parasites. The precise outcome may differ with site and/or nematode species.     

Two-spotted spider mite reared on resistant eggplant affects consumption rate and life table parameters of its predator,Typhlodromus bagdasarjani (Acari: Phytoseiidae)

The blue tick, Rhipicephalus microplus, threatens cattle production in most tropical and subtropical areas of the world. Delayed skin hypersensitivity reactions are thought to cause Nguni cattle to be more resistant to R. microplus than Bonsmara cattle yet the cellular mechanisms responsible for these differences have not been classified. Tick counts and inflammatory cell infiltrates in skin biopsies from feeding sites of adult R. microplus ticks were determined in 9-month-old Nguni and Bonsmara heifers to determine the cellular mechanisms responsible for tick immunity. Nguni heifers (1.7 ± 0.03) had lower (P < 0.05) tick counts than the Bonsmaras (2.0 ± 0.03). Parasitized sites in Nguni heifers had higher counts of basophils, mast and mononuclear cells than those in the Bonsmara heifers. Conversely, parasitized sites in Nguni heifers had lower neutrophil and eosinophil counts than those in the Bonsmara heifers. Tick count was negatively correlated with basophil and mast cell counts and positively correlated with eosinophil counts in both breeds. In the Bonsmara breed, tick count was positively correlated with mononuclear cell counts. Cellular responses to adult R. microplus infestations were different and correlated with differences in tick resistance in Nguni and Bonsmara cattle breeds. It is essential to further characterise the molecular composition of the inflammatory infiltrate elicited by adult R. microplus infestation to fully comprehend immunity to ticks in cattle.     

Cellular and chemical mediators of type 1 hypersensitivity in calves infected with Ostertagiaostertagi: Mast cells and eosinophils

Abomasal mucosal mast cell and eosinophil accumulation was morphometrically evaluated in 26 Holstein steers after natural or experimental infection with Ostertagiaostertagi. Results showed that following infection, accumulation of mast cells and eosinophils in abomasal tissue was dependent on infection pattern. Eosinophilia was greater in steers with type 1 ostertagiosis, while mastocytosis was more pronounced in steers with type 2 ostertagiosis.     

Studies on the inhibition of rejection of Trichostrongylus colubriformis larvae from immune sheep

A total of 8 drugs were examined for their ability to suppress the rejection of Trichostrongylus colubriformis infective larvae (L₃) from immune sheep. Specific antagonists of leukotrienes (plroxicam), prostaglandin (indomethacin) and the immunosuppressant cyclosporin A were given orally, while injectable preparations of dexamethasone, chlorpheniramine, BN 52051, WEB 2086 (anti-platelet-activating factor) and theophylline were administered as directed. The drugs were given for 5 days prior to and 4 days after challenge with 20,000 L₃, when worm counts were done. Corticosteroids inhibited rejection by around 70% in two experiments, and none of the remaining compounds were effective. In the third study, six of the drugs were given to susceptible sheep and did not affect the establishment of a primary infection with T. colubriformis.     

Haemonchus contortus and Trichostrongylus colubriformis did not adapt to long-term exposure to sheep that were genetically resistant or susceptible to nematode infections

We tested the hypothesis that Haemonchus contortus and Trichostrongylus colubriformis would adapt to long-term exposure to sheep that were either genetically resistant or susceptible to H. contortus. Sheep genotypes were from lines with 10 years prior selection for low (resistant, R) or high (susceptible, S) faecal worm egg count (WEC) following H. contortus infection. Long-term exposure of H. contortus and T.colubriformis to R or S genotypes was achieved using serial passage for up to 30 nematode generations. Thus, we generated four nematode strains; one strain of each species solely exposed to R sheep and one strain of each species solely exposed to S sheep. Considerable host genotype differences in mean WEC during serial passage confirmed adequate nematode selection pressure for both H. contortus (R 4900 eggs per gram (epg), S 19,900 epg) and T. colubriformis (R 5300 epg, S 13,500 epg). Adaptation of nematode strain to host genotype was tested using seven cross-classified tests for H. contortus, and two cross-classified and one outbred genotype test for T. colubriformis. In the cross-classified design, where each strain infects groups of R, S or randomly bred control sheep, parasite adaptation would be indicated by a significant host genotype by nematode strain interaction for traits indicating parasite reproductive success; specifically WEC and, for H. contortus strains, packed cell volume. We found no significant evidence of parasite adaptation to host genotype (P > 0.05) for either the H. contortus or T. colubriformis strains. Therefore, we argue that nematodes will not adapt quickly to sheep bred for nematode resistance, where selection is based on low WEC, although selecting sheep using a subset of immune functions may increase adaptation risk. Our results support the hypothesis that nematode resistance is determined by many genes each with relatively small effect. In conclusion, selection of sheep for nematode resistance using WEC should be sustainable in the medium to long-term.     

The relationship between ovine lymphocyte antigens and faecal egg count of sheep selected for responsiveness to vaccination against Trichostrongylus colubriformis

The purpose of this work was to determine if ovine lymphocyte antigen (OLA) type was associated with level of resistance and whether it could be used as a predictive test for identifying responsiveness of animals to vaccination against the parasite T. colubriformis. Antisera to ovine class I lymphocyte antigens were used to measure the frequency of three OLA types in merino sheep bred as either high or low responders to vaccination and challenge with T. colubriformis. A particular combination of lymphocyte antigens (SY la + lb) appeared to be associated with low faecal egg counts (resistant), and high faecal egg counts (susceptible) appeared to be associated with other OLA types, such as SY2. When high and low responder data were pooled, 56 ewes with SY la + lb, had a mean count of 149 eggs per gram (e.p.g) of faeces and 69 ewes with SY2 had 560 e.p.g. For 28 rams with SY la + lb, the mean count was 317 e.p.g. and 51 rams with SY2 had 1143 e.p.g. Overall these results were statistically highly significant. Separate analysis of each line showed that high responders, with SY la + lb had a mean count slightly below those with all other combinations within the same line, but this was not statistically significant. The SY la + lb type was not present in low responder males but in 11 low responder females this type was associated with significantly increased egg count. It was concluded that the case has yet to be proven that SY la + lb is a predictive marker for parasite resistance and not merely a foundation effect resulting from the selection and mating of particular sires.     

Cholecystokinin and anorexia in sheep infected by the intestinal nematode Trichostrongylus colubriformis

Symons L. E. A. and Hennessy D. R. 1981. Cholecystokinin and anorexia in sheep infected by the intestinal nematode Trichostrongylus colubriformis. Internationaljournal for Parasitology11: 55–58. It was postulated that there is a correlation between anorexia in intestinal nematode infection and the plasma concentration of cholecystokinin (CCK). In the first experiment plasma concentration of CCK rose as food consumption fell until, when sheep infected with Trichostrongylus colubriformis were almost completely anorexic, it had increased by 65%. Plasma CCK and food consumption returned to pre-infection levels in from four to six days after administration of an anthelmintic. In the second experiment food consumption by uninfected sheep was reduced in the first ten minutes after intravenous infusion of 150–300 μg of the octapeptide of CCK. It was concluded that anorexia in these infections may be due to or be mediated by higher concentrations of CCK.