The effect of selection of both sire and dam on the response of F1 generation lambs to vaccination with irradiated Trichostrongylus colubriformis larvae

Windon R. G. and Dineen J. K. (1981). The effect of selection of both sire and dam on the response of F₁ generation lambs to vaccination with irradiated Trichostrongylus colubriformis larvae. International Journal for Parasitology11: 11–18. Rams and ewes, tested for responsiveness to vaccination with irradiated T. colubriformis larvae at an early age, were mated on the basis of responder × responder and non-responder × non-responder. Progeny were vaccinated at 8 and 12 weeks of age with 20,000 irradiated larvae, treated with anthelmintic at 16 weeks and challenged with 20,000 normal larvae at 17 weeks. Faecal egg counts of progeny from responder matings were significantly lower than progeny from non-responders, and within each mating type, ewe lambs had markedly lower egg counts than ram lambs. The level of circulating complement-fixing antibodies to T. colubriformis larval extract were inversely related to egg counts. Thus, ewe progeny from responder matings had the highest serum antibody levels, non-responder ram progeny had the lowest levels and responder rams and non-responder ewes had similar intermediate levels. In vitro responses of cells stimulated with T. colubriformis L₃ antigen were greater in progeny from responder matings, whereas responses to bacterial lipopolysaccharide were higher in progeny from non-responder matings. The results confirm that the response to vaccination at an early age is genetically determined, and show that the response of progeny is most vigorously expressed when both sires and dams have been selected.     

The role of thresholds in the response of lambs to vaccination with irradiated Trichostrongylus colubriformis larvae

A piecewise logarithmic model fitted to worm counts of ewe lambs vaccinated and challenged in pens with a range of doses of irradiated and normal Trichostrongylus colubriformis larvae respectively, indicated that the threshold for response to both vaccine (V₀ = 4400) and challenge dose is exceeded by 5000 larvae. Whereas response was vaccine dose dependent, it was independent of challenge dose.Ram lambs vaccinated at low dose levels were as resistant against challenge as ewe lambs, but by contrast, failed to show increased protection after vaccination with high doses of irradiated larvae.Serum titre of antiworm complement-fixing antibodies at the time of challenge also indicated that ram lambs were less responsive immunologically than ewe lambs following vaccination at the higher dose levels.A field study showed that response to vaccination was only apparent after transfer of the sheep to heavily contaminated pastures, suggesting that previous exposure of the vaccinated animals to the low dose of infective larvae available on a lightly contaminated pasture constituted a challenge which was below the threshold.     

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 response of lambs to vaccination and challenge with Trichostrongylus colubriformis: Effect of plane of nutrition on,and the inter-relationship between,immunological responsiveness and resistance

Wagland B. M., Steel J. W., Windon R. G. and Dineen J. K. 1984. The response of lambs to vaccination and challenge with Trichostrongylus colubriformis: effect of plane of nutrition on, and the inter-relationship between, immunological responsiveness and resistance. International Journal for Parasitology14: 39–44. Merino lambs weaned at 8 weeks of age were fed either ground and pelleted (high plane, HP) or chopped (low plane, LP) lucerne hay ad libitum to achieve an approximate 2-fold difference in liveweight gain. When aged 17 and 21 weeks, 15 of the 20 lambs in each diet group were vaccinated with 80,000 irradiated T. colubriformis larvae. At 25 weeks, vaccinated and unvaccinated lambs were treated with anthelmintic and one week later challenged with 30,000 normal larvae. Four weeks after challenge the animals were killed for worm counts. After vaccination HP lambs had higher titres of antibodies to the parasite and after challenge had lower worm egg outputs, and lower worm burdens than LP lambs. Immunological responsiveness (serum titre of complement-fixing antibodies against worm antigen) and manifestations of resistance (eggs produced per female worm per day and percent protection calculated from worm counts) were significantly correlated within dietary groups. Percent protection and egg production per female worm were highly correlated (r = ?0.81) in individual animals pooled over dietary groups, suggesting that both manifestations of resistance respond to essentially the same immunological mechanism. Failure to obtain significant correlation between weight gain pre-vaccination and immunological and resistance parameters indicated that animal production and resistance to infection are not genetically linked. Negative correlation of weight gain during the vaccination period with serum antibody titre at challenge suggests that the developing immune response competes with weight gain for limited physiological resources of the animal.     

The initiation of coiling behaviour prior to desiccation in the infective larvae of Trichostrongylus colubriformis

Wharton D.A.1981. The initiation of coiling behaviour prior to desiccation in the infective larvae of Trichostrongylus colubriformis. International Journal for Parasitology11: 353–357. Infective larvae of Trichostrongylus colubriformis coil during the evaporation of water films. Decreasing the depth of the liquid film does not initiate coiling but enclosure in capillary tubes of similar diameter to the track width of actively swimming or crawling larvae results in a marked stimulation of coiling behaviour. It is suggested that larvae coil in response to the progressive restriction of lateral movement in an evaporating water film. The behavioural flexibility of the infective larvae of T. colubriformis maximizes both their survival and their chances of infection.     

The effect of osmotic stress on behaviour and water content of infective larvae of Trichostrongylus colubriformis

The role of the cuticle and sheath in the water dynamics of the infective larvae of Trichostrongylus colubriformis under osmotic stress and the effect of osmotic stress on behaviour have been investigated. In hypotonic solutions larvae lose the activity response to mechanical stimulation and there was also some increase in coiling. Larvae can regulate their water content in hypotonic solutions but lose water slowly in hypertonic solutions. Removal of the sheath by exposure to sodium hypochloritc or to a ‘natural’ stimulus had little effect on the water dynamics of infective larvae. The sheath thus appears to be freely permeable to water when hydrated whereas the cuticle has a very restricted permeability.     

Histamine and leukotriene concentrations in duodenal tissue and mucus of lambs selected for high and low responsiveness to vaccination and challenge with Trichostrongylus colubriformis

Lambs selectively bred for high responsiveness or low responsiveness to vaccination with irradiated Trichostrongylus colubriformis were vaccinated and challenged. Duodenal tissue histamine concentrations in both high and low responder lambs were lower at 3 days than at 28 days after challenge. At 3 days after challenge, histamine concentrations were higher in both male and female high responder lambs than in low responder lambs whereas at 28 days concentrations were increased only in high responder females. At 3 days after challenge, histamine concentrations were generally lower in mucus than in tissues, but levels were again higher in mucus from high responder groups. In duodenal tissue at 3 days after challenge, leukotriene C₄ and B₄ concentrations were similar in high and low responder animals. At the same time, concentrations of both leukotrienes were higher in mucus than in tissues, with high responder female lambs having the highest concentration. It is suggested that increased levels of histamine and leukotrienes in mucus and tissue are associated with larval rejection or exclusion.     

The effect of acquired resistance on adult worms of Trichostrong ylus colubriformis in lambs

Dineen J. K. and Windon R. G. 1980. The effect of acquired resistance on adult worms of Trichostrongylus colubriformis in Lambs. International Journal for Parasitology10: 249–252. Wether lambs were classified as either responders or non-responders to vaccination and challenge with Trichostrongylus colubriformis. Worms recovered from these animals and unvaccinated controls were measured, eggs in utero counted and sex ratios (male/female) were determined for individual burdens. The results showed that all three parameters were reduced in responder lambs compared with non-responder and unvaccinated lambs and were positively correlated with worm counts in responder lambs whereas they tended to be negatively correlated with worm counts in non-responders and unvaccinated animals.These various effects of resistance on parasite development in responder lambs may be due to the action of endogenous inflammatory agents generated immunologically. On the other hand negative correlation between developmental parameters and worm burdens in non-responders and unvaccinated lambs suggests that development of parasites in heavy infections may be restricted by competition for a limiting physiological, spatial or nutritional resource of the host.     

Haemonchus contortus: Local and serum antibodies in sheep immunised with irradiated larvae

Smith W. D. and Christie M. G. 1978. Haemonchus contortus: lccal and serum antibodies in sheep immunised with irradiated larvae. International Journal for Parasitology8: 219–223. Two doses of Co⁶⁰ irradiated Haemonchus contortus protected 9-month-old sheep against a challenge infection of 10,000 normal larvae. This resistance was associated with increased concentrations of IgG antibodies in the serum as well as IgA and IgG antibodies in the abomasal mucosa.     

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.     

家蝇幼虫提取物对辐射小鼠的免疫调节作用

研究了家蝇Musca domestica幼虫提取物对辐射小鼠的免疫调节作用。测定了小鼠的脏器官指数,NK细胞活性,T、B淋巴细胞增值活性及小鼠血清SOD活性和MDA含量等指标。结果表明：经口给予一定剂量的家蝇幼虫提取物对辐射和未辐射小鼠的脾脏指数和胸腺指数变化有显著影响,均可提高NK细胞活性,T、B淋巴细胞增值活性及小鼠血清SOD活性,同时可降低小鼠血清中的MDA含量。结果显示家蝇幼虫提取物对辐射和未辐射小鼠均具有较好的免疫调节作用。     

Histamine and leukotriene concentrations in duodenal tissue and mucus of lambs selected for high and low responsiveness to vaccination and challenge with Trichostrongylus colubriformis

Lambs selectively bred for high responsiveness or low responsiveness to vaccination with irradiated Trichostrongylus colubriformis were vaccinated and challenged. Duodenal tissue histamine concentrations in both high and low responder lambs were lower at 3 days than at 28 days after challenge. At 3 days after challenge, histamine concentrations were higher in both male and female high responder lambs than in low responder lambs whereas at 28 days concentrations were increased only in high responder females. At 3 days after challenge, histamine concentrations were generally lower in mucus than in tissues, but levels were again higher in mucus from high responder groups. In duodenal tissue at 3 days after challenge, leukotriene C₄ and B₄ concentrations were similar in high and low responder animals. At the same time, concentrations of both leukotrienes were higher in mucus than in tissues, with high responder female lambs having the highest concentration. It is suggested that increased levels of histamine and leukotrienes in mucus and tissue are associated with larval rejection or exclusion.     

Studies of the responses of basophil and eosinophil leucocytes and mast cells to the nematode Trichostrongylus colubriformis: Comparison of cell populations in parasite resistant and susceptible guinea-pigs

Handlinger J. H. and Rothwell T. L. W. 1981. Studies of the responses of basophil and eosinophil leucocytes and mast cells to the nematode Trichostrongylus colubriformis: comparison of cell populations in parasite resistant and susceptible guinea-pigs. Internationaljournal for Parasitology11: 67–70. Basophil and eosinophil leucocytes and mast cells in T. colubriformis resistant and susceptible guinea-pigs were compared. There were significantly more circulating and small intestinal eosinophils in the resistant guinea-pigs. Intestinal eosinophils increased in both groups following infection with T. colubriformis but after 10 days the count in susceptible animals had only reached the pre-infection count in the resistant group. Pre-infection intestinal mast cell counts in the two groups were similar. Mast cell counts in susceptible guinea-pigs did not change during the period of observation but almost doubled within seven days of infection in the resistant animals.     

Protein synthesis in the whole body,liver, skeletal muscle and kidney cortex of lambs infected by the nematode Trichostrongylus colubriformis

Jones W. O. and Symons L. E. A. 1982. Protein synthesis in the whole body, liver, skeletal muscle and kidney cortex of lambs infected by the nematode Trichostrongylus colubriformis. International Journal for Parasitology12: 295–301. Tyrosine flux and the synthesis of protein in the whole body, liver, skeletal muscle and kidney cortex and of albumin in lambs infected with Trichostrongylus colubriformis and uninfected lambs fed ad libitum or pair-fed with the infected group, were measured by constant infusion of ¹⁴C-l-tyrosine. Live weight gain was lower in the infected than in pairfed lambs, but rates of whole body protein synthesis were similar in both groups. On the other hand, compared with control lambs, there was a faster rate of protein synthesis per unit of protein consumed in infected but not in pair-fed lambs. Rates of protein synthesis per unit of body weight in infected were higher than in pair-fed lambs, but similar to the rate in control lambs. The fractional synthetic rates (FSR) of albumin and liver proteins and the amount of liver protein synthesized per day were increased by infection. The FSR and amount of protein synthesized per day were depressed in skeletal muscle and kidney cortex. Anorexia did not explain any of these changes. Infection caused a loss of protein from each of these tissues, but this loss was due to anorexia in only the liver. There was generally good correlation between concentration of RNA per g fresh weight or per mg nitrogen and the FSR of protein. However, although the $\text{RNA}\text{DNA}$ ratio correlated well with synthesis in skeletal muscle, it was poorly correlated for liver proteins. The relationship between the rate of growth and protein synthesis in infected lambs is discussed.     

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.     

The response of sheep to parenteral vaccination and immunizing infections against the abomasal nematode, Haemonchus contortus

Adams D. B., Beh K. J. and Davies H. I. 1982. The response of sheep to parenteral vaccination and immunizing infections against the abomasal nematode, Haemonchus contortus. International Journal for Parasitology12: 445–449. Subcutaneous injection of relatively large amounts of unfractionated homogenates of adults plus infective larvae of Haemonchus contortus emulsified in complete Freund's adjuvant produced a degree of protective immunity when challenge infection was given eight weeks after the first or only dose of vaccine. In an attempt to improve acquired immunity, parenteral vaccination was either followed or preceded by a short immunizing infection with H. contortus, which was terminated by anthelmintic before patency. This treatment aimed at stimulating general responsiveness to worm antigens and invoking mucosal immunity in the abomasum. Disparate results were obtained; immunizing infections either increased immunity or made sheep more susceptible to challenge infection. In this latter situation, the unresponsiveness associated with primary infection with H. contortus may have been increased.     

The fate of multiple doses of infective larvae of Nematodirus battus in 8-month-old lambs and their effect on intestinal enzyme activity

Mapes C.J. and Coop R.L. 1973. The fate of multiple doses of infective larvae of Nematodirus battus in 8-month-old lambs and their effect on intestinal enzyme activity. International Journal for Parasitology3: 363–370. The fate of five daily doses of 60,000 infective larvae of Nematodirus battus was studied in 8-month-old lambs. On 18, 26 and 34 days after the last larval dose 4.0, 3.3 and 1.0 per cent of the total infective dose was recovered. Approximately 50 per cent of the worms recovered on these days were fourth-stage larvae. It is suggested that L5 and adult stages were preferentially lost from the hosts and that male worms were developing at a faster rate than the females. The populations of N. battus were smaller, contained higher proportions of fourth-stage larvae and shorter L5 and adult worms than those developing from similar infective doses in 3-month-old lambs. A transient decrease in alkaline phosphatase and maltase levels was found in the mucosa of the small intestine and was compared with the marked and persistent changes in mucosal enzyme activities found with similar infective doses in 3-month-old hosts.     

The attraction of larvae of Culex pipiens quinquefasciatus Say to ribonucleic acid and nucleotides

The positive chemotaxis of larvae of Culex pipiens quinquefasciatus in response to RNA or its degradation products has been demonstrated. It has further been shown that larvae are specifically attracted to certain nucleoside monophosphates. The observations are related to the known dietary requirements of mosquito larvae.     

The escape response of food-deprived cod larvae (Gadus morhua L.)

The escape response of Atlantic cod larvae (Gadus morhua) 25 and 47 days post hatch (dph) - either fed or deprived of food for three days - was studied. Larval escape responses were provoked by water movement from the suction of a fixed-position pipette. Escape latency, distance, speed, burst speed, and vertical and lateral escape angles were quantified using motion tracking software designed for 3-D silhouette video recordings. Escape performance, expressed as escape distance and escape speed, improved with age. The escape angles were normally distributed and highly variable, ranging from − 170° to 170° and − 40° to 105° for lateral and vertical escape angles respectively. No food deprivation-induced effects in any of the behaviours were found, suggesting that there are no condition-related behavioural effects (size-independent effects) in escape response performance after 3 d of food deprivation. This may reflect a negligible difference in the cost/benefit equation for fed vs. food-deprived larvae in performing an escape response when under attack.     

The use of a water-in-oil adjuvanted vaccine in an attempt to immunize lambs against Taenia ovis cysts in the presence of maternal antibody

An attempt was made to actively immunize lambs during the period when they had maternally-acquired antibody, so that there would be no time when lambs were susceptible to Taenia ovis infection. A slow-release water-in-oil adjuvanted vaccine containing T. ovis oncosphere products was used. Half the ewes were vaccinated prior to parturition and lambs were vaccinated at approx. 5 weeks of age. At necropsy, after challenge infection, vaccinated lambs had a mean of 39 cysts, compared to 131 in unvaccinated control lambs (p < 0.05), but there was no effect on development or survival of the established cysts. The presence of passively-acquired anti-oncosphere antibody at the time of vaccination did appear to influence the degree of antibody response, and the level of protection induced. However, there was no correlation between levels of antibody at vaccination and levels of protection induced, because of the considerable individual variation between lambs. In non-vaccinated control lambs, the serological response to challenge infection was also highly variable.Some vaccinated lambs developed a strong primary serological response and were mostly (5/7) fully protected. Lesser degrees of primary response in other lambs did not fully protect. All vaccinated lambs gave a rapid secondary response after challenge, but it was too late to be protective. The immunization procedure, although effective in some lambs and partially effective in most, cannot be recommended.