Periparturient Rise Research Articles

Vaccination of sheep against haemonchosis with H11, a gut membrane-derived protective antigen from the adult parasite: Prevention of the periparturient rise and colostral transfer of protective immunity

Pregnant ewes were immunised with a fraction highly enriched in the membrane glycoprotein antigen H11, isolated from the intestinal brush border of adult Haemonchus contortus. Immunity induced by immunisation was able to abolish almost completely (98–99%) the worm egg output from pregnant ewes challenged with ca. 10,000 infective larvae of H. contortus during the last trimester. Furthermore, lambs born and reared on vaccinated ewes had substantial antibody levels to H11 derived from maternal transfer. This antibody conferred moderate protection against a bolus challenge of ca. 3000 infective larvae of H. contortus in 5-week-old lambs.

Strongyle infections in sheep and goats under the traditional husbandry system in peninsular Malaysia

Faecal egg counts were used to study patterns of trichostrongyle infections in sheep and goats according to season, age, pregnancy and lactation on traditional farms in west Malaysia. Haemonchus contortus and Trichostrongylus spp. were the most important strongyles in sheep and in goats, H. contortus, Trichostrongylus spp. and Oesophagostomum spp. were most prevalent. The faecal egg counts of sheep and goats were apparently not influenced by the small seasonal climatic variations. Strongyle infections were acquired at an earlier age in sheep than in goats. Mean faecal egg counts decreased from the age of 8 months onwards in sheep while in goats this occurred from 12–18 months onwards. A periparturient rise in strongyle egg counts was observed in both animal species. Haemonchus contortus was mainly responsible for this rise in faecal egg counts. The results are discussed with reference to control of gastrointestinal strongyle infections in sheep and goats.

Periparturient Rise in the Excretion of Giardia sp. Cysts and Cryptosporidium parvum Oocysts as a Source of Infection for Lambs

The possibility of a periparturient rise (PPR) in the excretion of Cryptosporidium parvum oocysts and Giardia duodenalis-type cysts and its implications in the epidemiology of these 2 pathogens were investigated. Fecal samples were taken from 32 lambing ewes every 2 wk from 4 wk before lambing until 8 wk after the start of lambing. Samples from both ewes and lambs were examined with a quantitative immunofluorescence assay. Excretion of Giardia sp. cysts by ewes increased at 2 wk prepartum, peaked at zero and 4 wk postpartum, and returned to low levels at 6 and 8 wk postpartum. Some ewes also excreted C. parvum oocysts at the start of lambing. Excretion rates and intensities of Giardia sp. cysts by lambs were high, whereas those of C. parvum oocyst excretion were light. The PPR in excretion of Giardia sp. cysts by ewes was considered to be the major source of giardiasis for lambs. Excretion of C. parvum oocysts by ewes at parturition also played a role in initiating cryptosporidiosis in lambs.

Acute or chronic administration of prolactin alters ovine infections of Haemonchus contortus

Prolactin has been implicated as a modulator in the phenomenon of periparturient egg rise during ovine nematodiasis. In the first experiment, lambs (4 months of age) with patent infections (10 000 infective larvae) of Haemonchus contortus were injected daily (Days 28–39 post-inoculation (PI)) with prolactin (20 or 200 IU) or saline. Fecal egg concentrations and total daily egg production were monitored for each lamb. After 12 days, lambs injected with the lower dose of prolactin had the highest daily egg production. Fewer adult worms were collected from prolactin-treated lambs, and the female worms were larger than those from the saline-injected controls. Worm size and number were not correlated. In the second experiment, lambs were injected daily with ovine prolactin (25 IU) or saline. Five days after initiation of treatments, each lamb was inoculated with 3000 infective larvae of H. contortus. After 42 days of injections (Day 37 PI), prolactin-treated lambs had larger and fewer worms, with higher fecundity, than saline-treated controls. Increases in endogenous circulating prolactin during late pregnancy and lactation in ewes, therefore, might contribute to periparturient egg rise irrespective of the developmental stage of the parasite when the hormone exposure occurs.

Pathophysiology of the periparturient egg rise in sheep: a possible role for IgA

The relationship between anti-parasite IgA antibody levels in plasma and the periparturient egg rise in sheep was investigated. Ostertagia circumcincta larvae (5000 third stage larvae three times weekly) were administered to three groups of seven adult immune ewes from 12 weeks before until three weeks after lambing (group 1) or from six (group 2) or 14 (group 3) weeks before until three weeks before lambing. Seven additional ewes were not challenged (group 4 controls). Ewes in groups 1, 2 and 4 received anthelmintics 14 weeks before lambing. Challenge of the pregnant ewes with O circumcincta larvae resulted in substantial increases in faecal egg counts only during the periparturient period regardless of the larval dosing regimen. Furthermore, the periparturient rise in faecal egg counts was closely associated with a significant increase in anti-parasite IgA antibody levels in plasma. This rise in IgA antibody levels occurred at a time when IgA is transported from the gut to milk during early lactation. It is postulated that this may lead to a temporary reduction in abomasal antibody levels of ewes and hence permit the establishment of larvae and, or, the emergence and development of inhibited larvae and thereby lead to the periparturient rise in faecal egg count.

Gastro-intestinal parasitism of cattle in native pasture grazing system in Guadeloupe (French West Indies)

Gastro-intestinal parasitism of creole cows and calves, Limousin × creole cross calves and Brahman × creole cross calves was recorded during seasons of calving in a native grazing system in Guadeloupe, a wet tropical area. Calvings were pooled during the dry season for two herds and during the rainy season for two other herds. For each calving season, calves of one herd were drenched monthly with anthelmintic. A marked periparturient rise in egg excretion was observed in cows. Coccidial infection was always present in calves, but no clinical signs were observed. The main parasites during the first 2 months of life were Strongyloides papillosus and Toxocara vitulorum. Then, Haemonchus placei, Trichostrongylus spp. and Cooperia spp. were the dominant species encountered. Brahman cross calves were the most heavily infested animals. There was no clear reltionship between third stage larvae (L3) population size on pasture and worm burdens in calves, except during the second month of life. Despite medium levels of infestation, parasitism inhibited the growth of creole calves: −10.5 kg of bodyweight at weaning (−59 g day −1 of daily bodyweight gain from birth to weaning). The pathological effects of subclinical parasitism were confirmed by a lower packed cell volume and albuminaemia in parasitized calves than in treated calves.

Periparturient rise in faecal nematode egg counts in West African Dwarf sheep in Southern Ghana in the absence of arrested strongyle larvae

The nematode egg output of two groups of ewes, a pregnant test group (2–3 years of age) mated between March and April and a non-pregnant control group (5–6 years of age) was followed. The worm burdens acquired by worm-free ‘tracer’ lambs were also followed on the same pasture from March 1988 to February 1989. There was a significant difference ( P<0.05) in the magnitude of the egg output in the test group compared with the control group. In the test ewes, an initial rise in egg production occurred 2 weeks after lambing and was maintained for five consecutive months. Necropsy worm counts from the ‘tracer’ lambs revealed that pasture larval levels were directly related to the levels of rainfall. Adult nematodes ( Trichostrongylus colubriformis, Trichostrongylus axei, Haemonchus contortus, Oesophagostomum venulosum and Trichuris ovis), and some Moniezia expansa were present in almost all the lambs throughout the year, with the exception of January and February 1989. The absence of immature larvae in these lambs indicates that arrested development is not a feature of the life cycle of these species in Southern Ghana. The occurrence of a periparturient rise of nematode eggs in West African Dwarf ewes, a year-round breeder, means that susceptible lambs could be open to infection throughout the year. Control should, therefore, be conducted by treating ewes after lambing and restricting the breeding season to particular periods of the year.

Gastro-intestinal nematode infections in a goat breeding farm in North-Western Sri Lanka

Faecal egg counts were used to study patterns of nematode infestation of adult female goats and their offspring according to season, pregnancy and lactation or age on a goat farm (n = 2000) in north-western Sri Lanka. Average rainfall in the area is 825 mm and temperature is between 23 and 33 degrees C throughout the year. The only nematode species present on the farm were Haemonchus contortus and Oesophagostomum columbianum. In adult females the faecal egg output was not influenced by season and no significant periparturient rise was observed. In kids the egg counts rose from the third month of age onwards and reached the same levels as the adults by the fourth month. Post-mortem studies on a neighbouring farm indicated that hypobiosis was not present.

Pathophysiology of the periparturient egg rise in sheep: the role of prolactin

The involvement of prolactin in the periparturient rise in the faecal nematode egg count in sheep was investigated. Ostertagia circumcincta larvae (5000 third stage larvae three times weekly) were administered to adult immune ewes from three weeks before parturition to three weeks afterwards. Ten ewes were injected twice daily with 2-bromo-alpha-ergocryptine (bromocriptine), an antagonist of prolactin secretion, for two weeks starting two days after lambing while 10 ewes remained untreated. Bromocriptine treatment was initiated approximately two weeks pre partum in three other ewes. Plasma pepsinogen concentrations rose significantly by one week after the start of O circumcincta larval challenge in all the ewes but faecal egg counts remained negative until approximately one week post partum. Plasma prolactin concentration was reduced to a very low level in all bromocriptine treated ewes but this did not alter the dynamics of the periparturient rise in faecal egg counts. Neither cell-mediated nor humoral immunity of the ewes, as assessed by their sensitivity to BCG inoculation and by antibody titre raised against horse red blood cells, respectively, were impaired during the rise in faecal egg count, nor were these parameters altered by manipulation of plasma prolactin concentration. Lamb growth rate was not retarded by low plasma prolactin concentration in the bromocriptine treated ewes. These results are not consistent with the generally held hypothesis that elevated plasma prolactin concentration is directly associated with the periparturient rise.

Teladorsagia circumcincta egg output at the onset of natural and induced lactation in ewes

Nineteen ewes maintained under ‘worm-free’ conditions received anthelmintic and 1 week later were dosed on 5 days each week with 500 Teladorsagia circumcincta larvae for between 10 and 12.5 weeks. Faecal egg counts were determined twice weekly. There were three groups: pregnant (P) ewes ( n = 6) which each reared twin lambs, hormone-treated (H) ewes ( n = 7) which were not pregnant and were given exogenous hormones (dexamethasone, oestradiol-17β, progesterone) for 37 days to induce udder development and milk production, and untreated barren (B) ewes ( n = 6). The plasma concentrations of oestradiol-17β, prolactin and progesterone were measured. Starting 10–15 days before birth in Group P, there was a biphasic periparturient rise in egg count and the onset of the first peak in egg count preceded the parturient peak in plasma prolactin concentration by several days. Most Group H ( 5 7 ) and all Group B ewes remained highly resistant to Teladorsagia infection throughout, despite an induced rise in prolactin concentrations in Group H ewes. It was concluded that factors other than prolactin initiate the periparturient rise but that prolactin is one factor which maintains the response once lactation commences.

Effects of exogenous progesterone and/or prolactin on Haemonchus contortus infections in ovariectomized ewes.

Reproduction can alter the course of ovine nematodiasis; fecal nematode egg concentrations often increase near lambing and throughout lactation, a phenomenon referred to as the periparturient rise. To identify the host mechanisms that might link these disparate events, i.e. lactation and the fecundity of gastrointestinal trichostrongyles, ovariectomized ewes were injected daily with progesterone and/or prolactin, or saline. Progesterone treatment commenced 20 days before inoculation with Haemonchus contortus and prolactin was administered throughout the 30-day infection period. Ovariectomized ewes receiving prolactin during the experimental infection maintained higher daily fecal egg concentrations than the progesterone, progesterone/prolactin, or the control treatment groups. However, ovariectomized ewes that received 20 days of pre-inoculation exposure to progesterone, as well as prolactin during the infection, had greater numbers of nematodes that were larger than the other treatment groups. Thus, the sequential delivery of these hormones that are associated with the reproductive cycle in ewes produced some of the same results that occur during periparturient rise.

Trichostrongylid parasite populations in pregnant or lactating and unmated Florida Native and Dorset/ Rambouillet ewes

This study was undertaken to identify factors which might contribute to differences in the periparturient rise (PPR) in fecal egg counts observed in two sheep breeds. The population dynamics of naturally acquired trichostrongyle infections were studied in unbred and pregnant or lactating Dorset/Rambouillet and Florida Native ewes. The sheep grazed infective pastures in the fall and were housed from December until the end of the experiment in June. Fecal examination showed consistently higher egg counts in Dorset/Rambouillet sheep than in Florida Natives throughout the experiment. Lambing Dorset/Rambouillet ewes showed a significant periparturient rise (PPR) while the fecal egg counts of periparturient Florida Natives did not differ from controls of that breed. The total worm burdens and parasite species composition were determined in pregnant or lactating and unbred animals of each breed at about 65 and 125 days post-breeding and at approximately 6 weeks post-lambing. Dorset/Rambouillet ewes had significantly higher trichostrongyle burdens than Florida Natives throughout the experiment. At the point 6 weeks post-lambing, unbred Dorset/Rambouillet and Florida Native ewes had significantly lower worm burdens than lactating animals. When the developmental stages of the parasite were examined, pregnant animals of the two breeds were found to have fewer arrested larvae than unbred animals. These results suggest that although a distinct periparturient egg rise does not occur in Florida Native sheep, they may still be subject to some of the immunosuppressive changes associated with lactation.

Haemonchus contortus and other trichostrongylid infections in parturient, lactating and dry ewes

From autumn (April) to spring (November), groups of pregnant and dry Merino ewes grazed pasture contaminated with infective larvae of Haemonchus contortus, Ostertagia circumcincta and Trichostrongylus colubriformis. A periparturient rise in faecal egg counts occured in the pregnant ewes, following the maturation in early spring of arrested fourth-stage larvae of H. contortus and failure of pregnant ewes to expel the resulting adult worms. Peak egg counts were seen in September, just before lambinf. In dry ewes, egg counts were slightly elevated at the time of the rise in the pregnant ewes, but fell to very low levels as adult worms developing from previously arrested larvae were expelled. Lactating ewes acquired greater burdens of O. circumcincta and T. colubriformis than did dry ewes, but were equally refractory to new infections with H. contortus. It is therefore suggested that the impairement of immunity to helminth infection seen in reproductive ewes may be more specific than was previously envisaged.

Hypobiosis and the Periparturient Rise in Sheep

From a parasite viewpoint, therefore, hypobiosis is a most useful life cycle adaptation to ensure persistence and has been reported in most of the important nematode species parasitizing sheep in North America. It facilitates the synchronization of the nematode life cycle to changing host and environmental conditions. It also enables the parasite to have available large numbers of infective forms at points in the host life cycle that coincide with the presence of susceptible neonates, thus ensuring transmission. The accompanying periparturient rise seen with many of these species following development of hypobiotic larvae has very important implications for the planning of control procedures. Because it appears to be the major source of pasture contamination early in the grazing season, it is the prime source of infection for the lambs. These lambs can in turn serve to augment pasture contamination, leading to very heavy levels of pasture infectivity in late summer and fall. By scheduling anthelmintic treatments so as to suppress this rise in egg counts, pasture contamination can be kept to a minimum. More effective, less frequent dosing with anthelmintics is needed.

The periparturient rise in fecal egg counts in three strains of Florida native ewes and its value in predicting resistance of lambs to Haemonchus contortus

The periparturient rise in fecal egg counts in three strains of Florida Native ewes and its value in predicting resistance of lambs to Haemonchus contortus. International Journal for Parasitology 16: 185–189. Significant ( P < 0.05) differences in the magnitude of the periparturient rise in fecal egg counts (PPR) occurred in ewes of three strains of Florida Native sheep. Non-lambing ewes ( n = 12) and lactating University strain ewes ( n = 31), a strain selected over a 26-year period for parasite resistance by survival at pasture without anthelmintic treatment, had lower fecal egg counts than ewes of either Maxcy strain ( n= 17), a commercial strain treated regularly with anthelmintics, or Backlinie strain ( n = 16), a strain of Florida Native sheep that had some crossbreeding to Hampshire and Suffolk in their genotype and were regularly treated with anthelmintics. Whereas both Maxcy and Backlinie ewes showed a pronounced PPR, none occurred in non-lambing ewes ( n=12) and the slight rise in fecal egg counts observed in University ewes was not significantly different from that of the non-lambing ewes. Backlinie ewes having twin lambs ( n = 5) had a higher PPR than Backlinie ewes with single lambs ( n = 11) or Maxcy ewes with single lambs ( n = 15), but all three groups had higher PPRs than University ewes with single lambs ( n = 27). No differences occurred in fecal egg counts of non-lambing ewes regardless of strain. Six weeks after weaning fecal egg counts of all ewes were uniformly low regardless of strain or prior lactation status. Ram lambs born to these ewes showed no significant strain differences in Haemonchus contortus burdens after experimental infection, deworming with levamisole and reinfection, although University lambs ( n= 13) had lowest mean worm burdens at necropsy (2437) followed by Maxcy lambs ( n= 12, mean =3106) and Backlinie lambs ( n= 13, mean =3670). There was no significant correlation between worm burdens in these lambs and the magnitude of the PPR in their dams. Eight to 16 weeks after turn out to a common parasite-infested pasture ewe lambs ( n = 13) born to University ewes had lower fecal egg counts than similar ewe lambs ( n=8) born to Backlinie ewes. Prior to this time differences were not significant and egg counts were generally low. The magnitude of the PPR in their dams was not significantly correlated with fecal egg counts or PCVs of individual ewe lambs.

Temporal changes in steroids, prolactin and growth hormone in pregnant and pseudopregnant gilts during mammogenesis and lactogenesis

Estrogen, progesterone and prolactin are involved in control of mammary growth in all species studied to date. The primary hormonal change temporally related to mammary development in swine is the estrogen rise which begins on day 60 of pregnancy. However, hormonal regulation of mammary development in swine is poorly understood. Plasma was obtained at 15-day intervals (days 15–112) throughout pregnancy, day of parturition and day 4 of lactation to determine relationships between hormonal profiles and mammary development in swine. Fetal plasma was also obtained from day 60 until parturition. Additional gilts were made pseudopregnant and sampled on days 60, 90 and 112. Plasma samples were assayed for estrogens, progesterone, prolactin and growth hormone. Maternal profiles of estrone- and estradiol-sulfate, increased to 2.6 and 0.6 ng/ml, repectively on day 30 of pregnancy, with return to basal concentrations by day 45. Periparturient concentrations of estrone and estradiol did reach 13 and 2.6 ng/ml, respectively. Free estrogen concentrations (estrone and estradiol) did not change significantly at day 30, but were elevated to 6 and 0.7 pg/ml at parturition. Progesterone concentration fluctuated only slightly from a mean concentration of 25 ng/ml until the preparturient decline, resulting in concentrations of <5 ng/ml through day 4 of lactation. Prolactin and growth hormone concentrations remained at basal values (13 and 12 ng/ml, respectively) until the periparturient rise to 68 and 28 ng/ml. Total fetal estrogen concentrations rose steadily throughout the sampling period; progesterone declined through day 105, but rose significantly by day 112 of gestation. Fetal prolactin concentration rose slowly throughout the sampling period to reach 12 ng/ml by day 105 of gestation. The profile for fetal growth hormone differed from that of other fetal hormones, in that concentrations were above maternal values for the entire sampling period, and the profile was best fitted by a second order curve with the peak at day 90 (> 150 ng/ml). With the exception of estrone, hormonal concentrations in estrogen-treated pseudopregnant gilts did not differ from pregnant counterparts, demonstrating that pseudopregnant gilts are an excellent in vivo model to study estrogen effects on mammary development in swine.

Resistance of nonlambing exotic and domestic ewes to naturally acquired gastrointestinal nematodes

No breed differences in Haemonchus contortus burdens were found when nonlacfating exotic (St. Croix and Barbados Blackbelly), domestic (Finn-Dorset × Rambouillet) and 1 2 exotic- 1 2 domestic ewes grazed fall pasture, but all ewes had significantly ( p < 0.05) lower worm burdens at necropsy than tracer lambs grazing the same pasture. Florida Native ewes grazing the same pasture showed significantly ( p < 0.05) less packed cell volume (PCV) decrease and significantly ( p < 0.05) lower fecal egg counts than the other ewe breeds but were not available for necropsy. Tracer lambs had a significantly ( p < 0.05) greater PCV decrease and significantly ( p < 0.05) higher fecal egg counts than ewes. The results of this study suggest that breed differences in the periparturient rise in fecal egg counts of exotic and domestic ewes observed in an earlier study may have been caused by breed differences in the periparturient relaxation of immunity rather than breed differences in the ability to acquire immunity to worms.

A comparison of the periparturient rise in fecal egg counts of exotic and domestic ewes

Ewes of three exotic breeds (Florida Native, Barbados Blackbelly and St. Croix) showed no periparturient rise in fecal egg counts (PPR) when housed from late fall through lambing and weaning. Domestic breed ewes (Rambouillet and Finn-Dorset × Rambouillet) showed a pronounced PPR 6–7 weeks post-lambing while St. Croix × domestic ewes showed an intermediate PPR under similar conditions. There was no PPR in non-lambing ewes. In a second experiment, breed differences in the PPR were not as pronounced when ewes were allowed to graze a contaminated pasture after lambing. Florida Native, St. Croix and 3 4 St. Croix × 1 4 domestic showed lower PPRs than the remaining breeds (Barbados Blackbelly, F 1 hybrids of exotic and domestic breeds and domestic ewes), but the magnitude of the PPR was generally small in all breeds. No relationship was observed between hemoglobin genotype and PPR in either experiment. It was concluded that a low or absent PPR is an important manifestation of breed resistance in exotic ewes and that this may be useful as a marker for breeding parasite-resistant sheep.

Observations on the epidemiology of coccidial infections in sheep under varying conditions of intensive husbandry including chemoprophylaxis with monensin.

Coccidiosis occurs sporadically in lambs at about 6 weeks of age when oocyst output is very high in healthy as well as in diseased lambs. These experiments were designed to throw light on the source of infection and to correlate oocyst output in lambs and ewes with performance in lambs. In two experiments, one indoors on deep litter the other in outdoor paddocks, oocyst output (of different coccidial species), body weight and clinical state of lambs were recorded weekly. Oocyst output in ewes was also recorded, starting 1-4 weeks before lambing. Monensin was included in the concentrates of ewes and/or lambs, up to lambing or before and after lambing. No periparturient rise was detected in the oocyst output of ewes. Monensin drastically reduced oocyst output in animals receiving it. Oocyst output in lambs appeared to be little affected by the output of ewes around the lambing period, but was reduced if the ewes' output was kept low after lambing. Lambs receiving monensin tended to produce drier faeces but their weight gain was not significantly greater than that of controls. Eimeria crandallis was the predominant species in the lambs, followed by E. ovinoidalis and E. ovina.

Control of ovine gastrointestinal helminthiasis by the use of ‘clean’ grazing and strategic dosing in the field

Despite the widespread adoption of clean grazing systems in lowland sheep flocks, detailed parasitological investigations had not previously been carried out on such flocks. A trial was therefore conducted on two commercial flocks: a traditional permanent pasture flock (A) and one operating a system of clean grazing (B), and on an East of Scotland College flock (C) which had operated a clean grazing system for eight years. Ewe and lamb worm egg output, pasture larval levels and lamb liveweight gains were monitored and tracer lambs were grazed during July and August on each farm. Under clean grazing conditions on farm C all parasitological parameters were lower than on both commercial farms. However, in the commercial flocks comparable contamination was evident from midsummer onwards and tracer lambs grazed during August on farm B had significantly greater worm burdens than on the other two farms. The differences observed between the flocks were thought to be due to greater residual contamination by overwintered larvae in both commercial flocks while the higher worm burdens in August on farm B probably resulted partly from incomplete control of the periparturient rise in ewe faecal egg output and partly to autoinfection of the lamb crop. It was concluded that farm C grazing was the cleanest. Considerable contamination was present on farm A while farm B occupied an intermediate position which resulted in considerable worm burdens in lambs grazing during the latter part of the season.