Mean corpuscular haemoglobin concentration as haematological marker to detect changes in red blood cells in sheep infected with Haemonchus contortus

Haemonchus contortus is a nematode parasite that causes anaemia and affects the health of sheep. The mean corpuscular haemoglobin concentration (MCHC) is an excellent indicator to detect anaemia that could help to characterize resistant or susceptible lambs to gastrointestinal nematodes. The aim of this study was to evaluate the predictive value of MCHC in detecting changes in red blood cells and their relation to anaemia in lambs re-infected with H. contortus. An analysis of information was performed using 24 Pelibuey lambs previously infected in grazing, dewormed and experimentally re-infected with H. contortus. At the first haematological sampling (admission) the lambs were classified based on MCHC quartiles (Q). Subsequently, the lambs were housed for 56 days. Blood samples were taken every seven days to determine the haematological parameters using an impedance haematological instrument. Confidence limits were constructed with the records of the lambs that recovered their haematological parameters. Each quartile was analysed as a treatment in a repeated measures design over time. To know the optimal combination of sensitivity and specificity of MCHC to detect anaemia a curve of receiver operating characteristic (ROC) curve and the cut-off values were evaluated. In quartile 4 (Q4), lambs showed the highest faecal egg count (FEC, 764 eggs/g of faeces), mean corpuscular haemoglobin (17.0 pg) and MCHC (54.6 g/dL). This group also presented the lowest RBC values (5.8 × 10⁶/mL), haematocrit (HCT, 18.3%), total plasma protein (5.7 g/dL), and HGB (9.7 g/dL). The optimal point of MCHC with ROC curve was 42.4 (sensitivity 88.2% and specificity 86.5%); the area under the curve was 0.91 (CI 95%, 0.86-0.96). These results are related to the haematological effects caused by H. contortus in susceptible lambs. In conclusion, the highest FEC and lower HCT in Q4 are important elements of the haematological damage caused by H. contortus and could identify susceptible lambs.

Anthelmintic efficacy of trichlorfon and blood parameters of young lambs infected with Haemonchus contortus

In this study we evaluated the efficacy of trichlorfon against Haemonchus contortus, monitoring its influence on blood parameters and plasma enzymes of lambs with haemonchosis. A lamb group was orally treated with trichlorfon at 100 mg kg^-1 while the other group was untreated. Split-plot design analysis was performed with the lamb groups defined as plots while the subplots were the four periods (weeks) of collection. The trichlorfon treatment promoted a significant and effective reduction of fecal egg counts after one week, with efficacies > 99%. After 21 days of treatment, detected blood parameters and serum levels of plasma enzymes were normal. Additionally, serum albumin and urea concentrations increased to normal values, which were not observed in untreated lambs. The treatment with this organophosphate, using a correct oral administration, may represent an effective therapeutic alternative for sheep infected with multi resistant strain of H. contortus.

[Preliminary essays to the validation of FAMACHA© method in conditions of semi-arid Paraibano]

The gastrintestinal helmintiases occupy prominence place among factors that limit the farming goat in entire world, especially on tropical regions, where economical losses are more accentuated. The objective of this work was to evaluate FAMACHA© method utilization as an auxiliary strategy on the control of parasites of goats in semiarid paraibano. Moreover the clinical assistance, values of hematocrit and OPG were determinate to evaluate the relation between the exams. They were used 30 moxotó female goats, monthly evaluated for 90 days. The female goats that presented degree three of mucose in accordance to the FAMACHA© method do not need to be vermifuged in accordance with hematocrit and OPG values. The FAMACHA© method, although too indicated for use in goats, needs little adaptation to be best administered.

A preliminary report on the use of FAMACHA for haemonchosis in goats in the Eastern Cape Province of South Africa during the late autumn/early winter period

From May to July 2005 a study was conducted on the prevalence and effects of haemonchosis in goats farmed on communal grazing belonging to resource-poor farmers at two study sites, namely Mlungisi (26 degrees 53'E, 31 degrees 53'S) and Ezibeleni (26 degrees 58'E, 31 degrees 53'S), situated within the Chris Hani District Municipality in Eastern Cape Province of South Africa. The usefulness of the FAMACHA system for identifying goats needing treatment was confirmed. It allowed stock owners to identify badly affected goats accurately, as borne out by the agreement between FAMACHA scores and corresponding haematocrits.

Control of Haemonchus contortus in goats with a sustained-release multi-trace element/vitamin ruminal bolus containing copper

The objective of this study was to determine the effectiveness of a sustained-release multi-trace element/vitamin ruminal bolus (TEB) containing copper administered to mature does for control of gastrointestinal nematodes (GIN) during summer months and during late gestation. Haemonchus contortus was the predominant nematode during these trials. In Experiment 1, yearling Spanish does were untreated or administered TEB (n=11/group) on Day 0 (August 2005) prior to breeding. In Experiment 2, Spanish and Boer does were untreated or administered TEB 6 weeks before kidding. Fecal egg counts (FEC) and blood packed cell volume (PCV) were determined weekly between Days 0 and 42. In both experiments, FEC were reduced within 7 days in TEB-treated compared with untreated does. PCV was similar between treatment groups (Experiment 1) or tended to be lower in the TEB group (Experiment 2). GIN control did not persist more than 28 days. These studies suggest that TEB may be an effective means of GIN control in mature goats, but additional control measures may be necessary.

Anthelmintic activity of Azadirachta indica A. Juss against sheep gastrointestinal nematodes

Gastrointestinal nematode control has been performed through use of anthelmintics. However, the development of resistant populations has required research into new alternatives. There are popular reports about anti-parasitic activity of Azadirachta indica in animals and plants. The aim of this study was to evaluate the anthelmintic activity of A. indica after feeding sheep with the dried leaves. In this experiment, 40 sheep were allotted into four treatment groups. Group I received a treatment of A. indica dry leaves mixed in a concentrate at a rate of 0.1 g/kg dose for 3 months. Group II was treated with double the dose of Group I. Group III was treated with closantel (Diantel) at the manufacturer-recommended dose once at the beginning of the study and Group IV was not treated. To compare treatment effects, the following parameters were evaluated: egg count per gram of feces (EPG), worm burden, weight gain and haematocrit. EPG and worm burden results were statistically evaluated using the Kruskal-Wallis test. Haematocrit and live weight gain were submitted to analysis of variance (ANOVA) and the means evaluated by Tukey's test with 95% probability. None of the evaluated parameters of the treatment groups were statistically different when compared to the control group, demonstrating that, with the protocol used, A. indica has no anthelmintic effect.

Phenotypic characterization of Haemonchus contortus: a study of isolates from Sweden and Kenya in experimentally infected sheep

The effects of cold storage of infective third-stage larvae (L3) of different isolates of the parasitic nematode Haemonchus contortus were studied with respect to infectivity, pre-patent period and propensity for larval arrestment. Two complementary experiments were conducted with 2 groups of lambs, each animal being inoculated with 2000 L3 of either Swedish or Kenyan origin. In a first experiment, L3s were cold treated at 5 °C for 9 months prior to infection, whereas in a second experiment larvae were newly hatched. Individual faecal egg counts (FECs), and worm burdens were determined for each experiment. The results showed that the greatest differences were associated with the pre-treatment of larvae. The pre-patent period and the FECs differed significantly between the experiments but not between the isolates used in each experiment. However, the extent of hypobiosis was significantly different between the two isolates when fresh larvae were used (36% Kenyan isolate and 70% Swedish). The storage of H. contortus at 5 °C had no apparent effect on the infectivity of L3s, as high establishment ranging from 43 to 74% were observed, irrespective of isolates used. This study showed that H. contortus exhibited similar phenotypic traits regardless of geographical origin. Thus, there was limited evidence for adaptations to temperate climatic conditions.

Efficiency of feeding Duddingtonia flagrans chlamydospores to grazing ewes on reducing availability of parasitic nematode larvae on pasture

Gastrointestinal nematodes are of concern in sheep production because of production and economic losses. Control of these nematodes is primarily based on the use of anthelmintic treatment and pasture management. The almost exclusive use of anthelmintic treatment has resulted in development of anthelmintic resistance which has led to the need for other parasite control options to be explored. The blood sucking abomasal parasitic nematode Haemonchus contortus causes severe losses in small ruminant production in the warm, humid sub-tropic and tropics. This study evaluated the effectiveness of a nematode trapping fungus, Duddingtonia flagrans, in reducing availability of parasitic nematode larvae, specifically H. contortus, on pasture. Chlamydospores of D. flagrans were mixed with a supplement feed which was fed daily to a group of crossbred ewes for the duration of the summer grazing season. A control group was fed the same supplement feed without chlamydospores. A reduction in infective larval numbers was observed in fecal cultures of the fungus-fed group. Herbage samples from the pasture grazed by the fungus-fed group also showed a reduction in infective larvae. There were no significant (P > 0.05) differences in overall fecal egg count, packed cell volume or animal weight between fungus-fed and control groups. Tracer animals were placed on the study pastures at the end of the study to assess pasture infectivity. Although tracer animals were only two per group, those that grazed with the fungus-fed group had substantially reduced (96.8%) nematode burdens as compared to those from the control group pasture. Results demonstrated that the fungus did have activity against nematode larvae in the feces which reduced pasture infectivity and subsequently nematode burdens in tracer animals. This study showed that D. flagrans, fed daily to grazing ewes, was an effective biological control agent in reducing a predominantly H. contortus larval population on pasture.

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.

Haemonchus spp. in sheep farmed under resource-poor conditions in South Africa--effect on haematocrit, conjunctival mucous membrane colour and body condition

A longitudinal study was conducted on the differential faecal egg counts, haematocrits and body condition scores of sheep belonging to resource-poor farmers at Rust de Winter, Gauteng province, and Kraaipan, North West Province, South Africa. The animals were scored for level of anaemia using the FAMACHA method, an assay for the clinical evaluation of anaemia caused by Haemonchus spp. Periods of higher Haemonchus egg counts occurred from October to March for sheep at Rust de Winter and from September/October to February or April for sheep at Kraaipan. Lower haematocrit values were registered during these periods as was a higher incidence of anaemic conjunctival mucous membrane colour scores compared to the period April to September. No clear relationship between the faecal egg counts and the body condition scores was evident. Although wider application of the FAMACHA system in sheep raised by resource-poor farmers should be investigated, the present study indicates that this method may certainly prove to be a valuable worm control strategy for such livestock owners.

Incidence of Haemonchus spp. and effect on haematocrit and eye colour in goats farmed under resource-poor conditions in South Africa

The diversity and predominance of nematode genera in goats of resource-poor farmers at Rust de Winter, Gauteng Province, Impendle, KwaZulu-Natal Province, and Kraaipan, North-West Province, South Africa, was determined by means of a longitudinal study of the nematode faecal egg counts (FECs) and differential third-stage nematode larvae. The animals were bled for haematocrit determination and scored for pallor of ocular mucous membranes using the FAMACHA( Copyright) method, an assay for clinical evaluation of anaemia caused by Haemonchus spp. Animals considered to be in danger of dying from anaemia caused by haemonchosis were selectively treated with an anthelmintic. Lower haematocrit values were registered during periods of heavier Haemonchus infection, which occurred from December/January to March for Rust de Winter; from December to March/April for Impendle; and from November/December to February or April for Kraaipan. There was agreement too between the lower haematocrits and paler mucous membranes scored according to the FAMACHA( Copyright) method. The use of this system may be recommended as part of an integrated approach to worm control in goats kept in the resource-poor areas studied.

Potency of three Haemonchus contortus antigens in the diagnosis of ovine haemonchosis

One hundred faecal specimens and corresponding blood samples were evaluated for Haemonchus contortus infection in sheep by ELISA utilizing somatic, circulating and coproantigens. Results proved that coproantigen was more potent than the others in diagnosis of sheep haemonchosis. SDS-polyacrylamide gel electrophoresis demonstrated that the three antigens are structurally related. Immunoblot analysis revealed that somatic antigen contained 6 polypeptides of molecular weights 234, 205, 178, 83, 48 and 14 kDa, while, coproantigen showed 4 immunogenic polypeptides of 234, 205, 85 and 45 kDa. In circulating antigen only 2 polypeptides of molecular weights 165 and 99 kDa were immunoreactive. The potency of coproantigen may be attributed partially to one polypeptide of molecular weight 45 kDa. This low molecular weight polypeptide was only expressed in coproantigen as an immunogen, probably increases the immunogenicity, and may have potential diagnostic and protective values.

Clinical evaluation of anaemia in sheep: early trials

Trials were conducted on a farm in Mpumalanga Province in South Africa to test the possibility of grading the colour of the ocular mucous membranes of sheep as an indication of the extent to which the animals are affected by Haemonchus contortus infection. The range of observed colour shades were classified into five categories, from red, through red-pink, pink and pink-white to white. Over a period of 125 days routine drenching of a flock of 388 sheep on irrigated kikuyu (Pennisetum clandestinum) pasture was terminated. During this time the animals were examined at practically weekly intervals and haematocrit determinations done for all the sheep with pale conjunctivae. Only those sheep having a haematocrit of 15% or lower were treated. Compared to a previous drenching tempo of close to every 3 weeks during the Haemonchus season on the farm, drenching was reduced by approximately 90%, as 70% of the sheep did not require salvage drenching and only 10% of the flock had to be given more than one salvage treatment. At the time of the trial the five clinical classifications were not related to predetermined haematocrit categories. However, when compared to categories that were set in later trials, 94% of the clinical estimates in the present trial were either in the correct haematocrit category, or, if not, the sheep were probably not disadvantaged by the errors. In 2.6% of cases the incorrect estimate may have placed the sheep concerned in jeopardy, as the haematocrit values were so low that salvage drenching was required, while the sheep were not regarded as anaemic. Changes in the mean haematocrit values of drenched and undrenched sheep were mirrored reciprocally by the changes in clinical colour estimates. Lactating ewes were by far the most susceptible class of sheep, as only 44.6% of them were able to manage without drenching, compared to 83% of dry, and 70.6% of pregnant ewes. Correlations between the haematocrits and clinical estimates were highly significant, although the associations were not high enough to give reasonable surety that the haematocrit values of individual animals could be predicted with confidence from their clinical classifications. Exceptionally large numbers of worms were recovered from seven of the 14 sheep that were culled because of age at the end of the trial, but these were reflected neither in their faecal worm egg counts, nor, with one exception only, in clinical signs.

A preliminary study on the anthelmintic activity of Calotropis procera latex against Haemonchus contortus infection in Najdi sheep

The anthelmintic activity of Calotropis procera latex was investigated in sheep that had been infected with single oral doses of 12000 infective Haemonchus contortus larvae. Inappetence, dullness, erosive abomasitis, decreased haemoglobin concentration and increased eosinophils were the main features of haemonchosis in the sheep. In the sheep treated with single oral doses of 0.01 ml or 0.02 ml/kg body weight of C. procera latex, egg production was significantly reduced, but not completely suppressed, and fewer adult Haemonchus worms were found in the abomasum. Although the appetite improved, the haemoglobin concentration and serum copper, iron and zinc levels were still reduced after therapy with Calotropis latex. Calotropis latex showed a concentration-dependent larvicidal activity in vitro within 20 min of application.

The response of Nigerian West African Dwarf goats to experimental infections with Haemonchus contortus

One option for controlling haemonchosis in warm pastoral regions is improvement of resistance by selective breeding. Variation in acquired immunity to H. contortus and immunological correlates of infection were studied in West African Dwarf (WAD) goats. Following exposure to 5000 L3, 63 per cent of the inoculum established but 77 per cent of established worms were expelled by week 5. All infected animals were anaemic (day 14). When exposed to 2000L3, 36 per cent of the inoculum was still present (day 35) with no loss by day 49. Persisting primary infection worms survived a superimposed challenge (day 35), but their growth was slowed and resistance to challenge was significant. Most goats showed eosinophilia and parasite-specific IgG responses to primary infection, but only eosinophilia increased after challenge. No consistent associations were found between parasite burden and any immunological measures of infection, but parasite egg counts showed considerable variation. Overall, our results suggest that resistant genotypes exist among the WAD goat population.

Protein supplementation improves the performance of parasitised sheep fed a straw-based diet

A study was made of the benefits of protein supplementation for parasitised and non-parasitised lambs. Sixty, 5-month-old crossbred wether lambs were placed in individual pens indoors for 9 weeks. Half of the animals were experimentally dosed with 1500 Haemonchus contortus larvae per head per week and were fed ad libitum and the other half were worm-free, pair-fed controls. Diets were formulated to be iso-energetic (9.0 MJ of calculated metabolisable energy per kg dry matter) with five levels of protein (10, 13, 16, 19 and 22% crude protein). These diets were based on oaten chaff, with barley, cotton-seed meal, urea and mineral mix (except for the 22% crude protein diet which did not contain barley). Dietary crude protein content increased live-weight gain, feed intake, rumen fluid ammonia-N, packed cell volume, eosinophil counts and antibody responses to H. contortus L3 antigen and decreased faecal worm egg counts significantly. Infection did not significantly affect packed cell volume of animals on diets with 16, 19 and 22% crude protein content. We conclude that extra dietary protein can prevent the adverse effects of H. contortus infection on animal production.

Repeated infections with Haemonchus contortus and Trichostrongylus colubriformis in dairy goats: comparison of resistant and susceptible animals

A total of 70 strongyle-free French Alpine dairy goats were exposed to a combination of sequential and challenge infections with Haemonchus contortus and Trichostrongylus colubriformis third-stage larvae. The sequential infection consisted of three inoculations at 50-day intervals, each infection being abbreviated by anthelmintic treatment at 40 days postinoculation. The challenge infection, composed of the same nematode strains, was undertaken 2 months later, when goats were at their 1st month of lactation. Fecal egg counts (FECs), packed cell volumes (PCVs), pepsinogen concentrations, inorganic phosphate concentrations, and peripheral eosinophil numbers were measured at 30-40 days after each inoculation. Goats were defined as being resistant or susceptible according to their level of nematode egg output following the first inoculation. Significant differences in FECs were recorded between the two groups throughout the further inoculations and the challenge infection. The reliability of FECs was supported by the high repeatability values found within and between infections. With regard to blood constituents, only PCVs related to H. contortus infection showed values that differed significantly between the two groups, resistant goats having higher PCVs after the first and the third inoculations than did susceptible animals. However, this difference was not detectable after the challenge infection. The milk production yield for the current lactation was significantly lower in the resistant goats. Moreover, resistant animals exhibited constantly greater body condition scores as compared with susceptible animals. These results indicate that the individual responsiveness of dairy goats to experimental nematode infection can be estimated on the basis of FECs and PCVs (for H. contortus) and is negatively related to the level of milk production of the animals.

Haemonchosis in Spanish ibex

Two cases of haemonchosis occurred in the Spanish ibex (Capra pyrenaica) population of the National Hunting Reserve of Tortosa and Beseit, northeastern Spain, in July 1992 and May 1993. The animals were cachectic and recumbent and had an acute hemorrhagic, macrocytic and hypochromic anemia; which was related to a high infection of 2,016 and 1,863 Haemonchus contortus, respectively, in the abomasum of the animals.

Vaccination against Haemonchus contortus with denatured forms of the protective antigen H11

As part of a systematic examination of the protective epitopes on H11, groups of sheep were vaccinated with preparations of purified H11 used untreated (group A), or progressively denatured (linearized) by incubation with sodium dodecyl sulphate (SDS) (group B) or by boiling with SDS in the presence of dithiothreitol (group C). All the sheep developed antibodies which bound to the untreated H11. When challenged with 10,000 infective larvae of Haemonchus contortus the mean levels of protection relative to the mean values for adjuvant controls were 99.8%, 85% and 79% for faecal egg counts and 95%, 79% and 54% for worm burden at post-mortem for groups A, B and C respectively. The H11-specific antibodies inhibited the microsomal aminopeptidase activity of H11 in vitro up to 80%. The levels of inhibition by sera from individual animals correlated with levels of protection with r2, of 0.69-0.87.

Modified plasma and abomasal disposition of albendazole in nematode-infected sheep

The influence of gastrointestinal nematode infection on the kinetics of albendazole (ABZ) and its metabolites, albendazole sulphoxide (ABZSO) and sulphone (ABZSO2) in plasma and abomasal fluid was investigated in sheep. A micronised suspension of ABZ was administered intraruminally at 7.5 mg kg-1 to the following groups of sheep: (a) non-parasitised (control); (b) artificially infected with Haemonchus contortus; (c) naturally infected with Haemonchus contortus and other species of gastrointestinal nematodes. Plasma and abomasal fluid samples were obtained serially over 72 h post-treatment and they were analysed by HPLC for ABZ and its metabolites. The ABZ parent drug was not detected in plasma at any time post-treatment, however the metabolites ABZSO and ABZSO2 were recovered in the bloodstream. The active metabolite ABZSO was recovered in plasma between 0.5 and 48 (uninfected), 60 (H. contortus infected) or 72 h (naturally infected sheep) post-administration. The area under the plasma concentration vs time curve (AUC) values for ABZSO were higher in both artificially infected (64.0 micrograms h ml-1) and naturally infected (79.3 micrograms h ml-1) sheep as compared with non-infected animals (41.8 micrograms h ml-1). Peak plasma concentrations for ABZSO and ABZSO2 were higher in both artificially and naturally infected sheep than in non-parasitised animals. No changes in the half-lives and mean residence times for these metabolites were observed in infected sheep. ABZ and its metabolites were found in the abomasum between 0.5 and 48 (infected animals) or 72 h (uninfected) post-treatment. The availability (total AUCs) of ABZ and its metabolites in abomasal fluid were lower in H. contortus infected sheep than in the uninfected control animals. The increased abomasal pH induced by the presence of the H. contortus infection may reduce the plasma/abomasum pH gradient, which results in a decreased ionic-trapping of ABZ and its metabolites in the abomasum. Such a phenomenon correlates with: (a) the higher total AUC values obtained for ABZ metabolites in the bloodstream of the infected compared to the control sheep, (b) the lower concentration profiles of the ABZ parent drug and its metabolites found in the abomasal fluid of the infected animals.

Genetic resistance of three genotypes of goats to experimental infection with Haemonchus contortus

A total of 46 weaned kids of three genotypes aged about 4-5 months were used to evaluate the effects of trickle infection with a sheep strain of Haemonchus contortus. A completely randomized 3 x 2 factorial design was used. Factors were genotype (Thai native (TN), 75% TN x 25% Anglo-Nubian (AN) and 50% TN x 50% AN) and parasite (control and infected). The animals were infected with 750 infective larvae (L3) of H. contortus three times a week for 3 weeks, with a total of 6750 larvae. The experiment lasted 9 weeks. Each week animals were weighed, faecal egg counts done and blood examined for haematological and biochemical variables. Twenty-seven kids were slaughtered at the end of experiment for worm recovery. Weight gain of infected animals was lower than those of uninfected controls (P < 0.05). The genotype 50% TN x 50% AN had higher growth rate than TN and 75% TN x 25% AN genotypes (P < 0.05). Eggs per gram of faeces (EPG) were significantly higher in 50% TN x 50% AN kids than in TN (P < 0.0005) and 75% TN x 25% AN (P < 0.0001) kids. There was a large variation in the EPG of individual animals within a genotype. The percent establishment of L3 was 8.2% in TN, 16.97% in 50% TN x 50% AN and 17.91% in 75% TN x 25% AN kids. TN kids had worm counts lower than 50% TN x 50% AN (P < 0.05) and 75% TN x 25% AN (P = 0.07) kids. Infection had a significant effect on packed cell volume (PCV), haemoglobin, total protein and albumin. The decrease in the level of these blood parameters was less in TN kids than in 50% TN x 50% AN and 75% TN x 25% AN kids. There was no significant difference between genotypes in the values of total and differential leucocyte counts and mean corpuscular volume (MCV). It can be concluded that TN goats are more resistant to H. contortus than 50% TN x 50% AN goats. However, under the present experimental conditions, the liveweight gain of 50% TN x 50% AN was higher than the TN goats.

Response of Dorper and red Maasai lambs to trickle Haemonchus contortus infections

Six-month-old red Maasai lambs were more resistant than Dorper lambs to repeated infections at one to two week intervals with 1000 Haemonchus contortus infective larvae. Resistance after infection was assessed by means of faecal egg counts, packed cell volumes, eosinophil counts, total serum protein concentrations and mortality rates. The weight gains of the infected animals were only marginally lower than those of their uninfected controls, most probably because of their significantly higher feed consumption, and evidently the infected lambs were not utilising all of the extra feed for growth. This absence of anorexia in spite of the infection was probably due to the palatability of the high protein diet fed to the lambs.

A comparison of the responses to repeated experimental infections with Haemonchus contortus among Scottish Blackface lambs

Twenty helminth-naive Scottish Blackface lambs were given three infections with 10,000 infective larvae of Haemonchus contortus at 8 week intervals. An additional six lambs served as uninfected controls and eight lambs were infectivity controls. The lambs were 7 months old at the start of the infection. Four of the 20 lambs developed severe haemonchosis and were put down during the experiment. The remaining 16 lambs plus uninfected controls were necropsied 8 weeks after the third infection. The mean faecal egg count peaked 6-8 weeks after the first infection, gave a second smaller peak 6-8 weeks after the second infection but produced no peak after the third infection. Mean red blood cell counts fell rapidly during the first infection, then rose gradually during the second and third infections. The mean values suggested that two infections were sufficient to produce effective immunity in the sheep population but they masked considerable individual variation. Eleven animals appeared relatively resistant following the first infection, while two animals were relatively susceptible to even the third infection. The repeatability of mean faecal egg counts or mean red blood cell counts for each animal during the replicate infections were very high, because the rankings of the individual sheep remained remarkably stable. Faecal egg counts were very strongly correlated with red blood cell counts. Multiple regression analysis showed that four factors--faecal egg counts, red blood cell counts, weight and sex--accounted for essentially all of the observed variation in worm burdens among the lambs. Therefore, under these controlled experimental conditions, additional markers appear unnecessary for the detection of resistance status.

Influence of supplementation with dietary soyabean meal on resistance to haemonchosis in Hampshire down lambs

The influence of dietary protein supplementation on resistance to haemonchosis was examined in Hampshire down lambs fed either a basal diet or a diet supplemented with soyabean. At seven months of age the lambs were challenged with an initial loading dose of Haemonchus contortus, followed by a trickle infection three times a week. Blood and faecal samples were collected three times a week and bodyweights were recorded weekly. After 10 weeks the lambs were slaughtered and their worm burdens and carcase composition determined. Although their mean worm burdens were similar, the lambs given the basal diet had higher faecal egg counts, lower packed red cell volumes and lower concentrations of total plasma protein and plasma albumin than the lambs given the supplemented diet. The dietary supplementation also improved the carcase composition of the lambs.

[The behavior of hematological parameters (hemoglobin, hematocrit, leukocyte count) and clinicochemical values in plasma (glucose, total proteins, alpha-amino-N, urea, pepsinogen, ascorbic acid, Fe, Cu, Zn) and the content of ascorbic acid in liver, spleen and adrenal glands in healthy lambs and lambs infected with Haemonchus contortus and Trichostrongylus colubriformis]

In 8 healthy, noninfected lambs with an initial body weight (b. w.) of 24.79 +/- 1.16 kg as well as in 3 groups of lambs (n = 8 per group) of a similar body weight after an inoculation with 3rd stage larvae of Haemonchus contortus (2500) and Trichostrongylus colubriformis (10,000) analyses of the blood plasma were performed for 45 days thereafter. On the 37th day after infection ivermectin (0.2 mg/kg b. w.) was administered per os respectively subcutaneously to the lambs of 2 groups. After 7 and 8 days the content of ascorbic acid in the liver, the spleen and the adrenals as well as that of vitamin A in the liver was analysed. The behaviour of the values influenced by a moderate infection with trichostrongylid nematodes is discussed.

Systemic responses to challenge infection with Haemonchus contortus in immune Merino sheep

Some systemic responses to single-dose infection with 10,000 Haemonchus contortus infective larvae were examined in sheep already shown to have protective immunity against the parasite. The major haematological finding was a neutrophil leukocytosis that occurred after the infections became patent but not during the pre-patent period. There was no definitive eosinophilia and no discernible change in the erythrocyte parameters. Systemic hyperthermia was not conclusively evident during the pre-patent period. Enzyme-linked-immunosorbent assays (ELISA) were used to measure the secondary anti-helminth antibody response in serum during the pre-patent period when the establishment of patent infection is resisted. These ELISAs employed preparations from adult worms to represent the parasitic stages of the worm, preparations from infective larvae to represent the pre-parasitic stages of the worm, and exsheathing fluid, which is the soluble material obtained when H. contortus larvae undergo ecdysis and transform from the pre-parasitic to the parasitic phase. Antibody responses to the three preparations differed qualitatively, indicating the presence of three different but perhaps overlapping sets of antigens. The three peaks in antibody against exsheathing fluid may reflect the pulses of antigen delivered to sheep as the parasite undergoes its three moults within the host.

Interaction of parasitism and nutrition in goats: effects on haematological parameters, correlations, and other statistical associations

Weaned wether goats (n = 144) approximately 6 months of age were placed in a 2 x 3 factorial experiment to test the effects and interaction of two levels of nutrition (growth+maintenance, NUT1; and twice growth+maintenance, NUT2) and three levels of Haemonchus contortus burden (0, 500, and 2000 larvae administered every 2 weeks; W0, W500, and W2000, respectively) on packed cell volume, red blood cell count, total serum protein and leukocytes. The statistical analysis revealed clear and proportionate differences among levels of infection for all variables. A significant (P < 0.05) nutritional effect was also found associated with all the variables except leukocytes. Nutrition by worm load interactions were found for packed cell volume and leukocytes. The neutrophil/lymphocyte ratio was higher in the NUT1-infected animals, leading to the nutrition by worm load interaction for leukocytes. An analysis for the different leukocyte types revealed significant (P < 0.05) differences among infection levels for lymphocytes, while nutrition level was found to be a significant effect for basophil count and immature white cells. Several significant correlations were observed between pairs of variables. Faecal egg output could be predicted from actual worm count in three of the four necropsy periods. The clear differences observed for blood parameters were not present in production traits, suggesting that physiological thresholds may play an important role in framing the metabolic activity of biological organisms. Total serum protein was the best indicator of these effects on production parameters.

An association of faecal egg counts and prolactin concentrations in sera of periparturient Angora goats

Faecal egg counts and serum prolactin concentrations in 13 pregnant and five non-pregnant Angora goats were monitored over a period of 20 weeks. The mean weekly egg counts of pregnant goats were significantly higher (P less than 0.01) than those of non-pregnant goats. In pregnant goats the mean egg counts in the 6 week post-partum period were significantly higher (P less than 0.01) than those of 6 weeks prepartum. The mean prolactin concentration of pregnant goats during the 6 week post-partum period was significantly higher (P less than 0.01) than that of 6 weeks pre-partum. During the 6 to 3 weeks before parturition, the prolactin values generally remained low (below 100 ng ml-1). The rise in prolactin concentration started between 3 weeks and 1 week before parturition. Only in pregnant goats was there a positive linear regression between prolactin levels and faecal egg counts.

Blood gastrin and pepsinogen responses of native village goats in Malaysia to infection with Haemonchus contortus

Blood gastrin and pepsinogen responses of native village goats in Malaysia to a single dose of 10,500 infective Haemonchus contortus larvae were investigated. Both blood values were significantly elevated within a week of infection and exhibited a highly significant correlation during the study. The magnitude of the blood gastrin response was, however, significantly greater than that of pepsinogen during the period that both blood values were elevated. It is suggested that blood gastrin assay may be of particular value in the diagnosis of chronic haemonchosis in animals harbouring relatively light worm burdens.

Changes in liveweight gain, blood constituents and worm egg output in goats artificially infected with a sheep-derived strain of Haemonchus contortus

Two groups of goats were dosed with 10,000 and 20,000 sheep-derived strain (SDS) larvae of Haemonchus contortus respectively. Over a period of 42 days goats dosed with 20,000 larvae lost more weight than those dosed with 10,000 larvae. Infected goats showed anaemia from about 2 weeks after infection as well as reduced levels of total serum proteins and albumins.

Pepsinogen types in worm-free sheep and in sheep infected with Ostertagia circumcincta and Haemonchus contortus

Pepsinogen isolated from the plasma of Dorset wethers with abomasal burdens of Ostertagia circumcincta was found to have the same proportions of three zymogen subtypes as that isolated from the plasma of Merino wethers with abomasal burdens of Haemonchus contortus. It appears that the underlying pathophysiological response which causes increased plasma pepsinogen concentrations during abomasal parasitism may be the same irrespective of the breed of sheep or species of parasite.

Hypergastrinaemia of sheep infected with Haemonchus contortus

Radioimmunoassay of plasma gastrin has shown that a hypergastrinaemia occurs in yearling sheep, after infection with 10(6) infective third stage larvae of Haemonchus contortus. Plasma gastrin concentrations began to rise two to four days after infection, that is, at about the same time as, or slightly before, the abomasal pH was observed to increase.

Influence of dietary protein on the pathophysiology of haemonchosis in lambs given continuous infections

Mixed-sex groups of three-month-old Finn Dorset and Dorset Horn lambs were given complete diets containing either high or low protein. A trickle infection with Haemonchus contortus of 200 larvae, given three times a week, began one month later for a 17 week period. Erythrokinetic, metabolic, digestibility and balance studies were conducted with the male lambs during weeks 12 to 14 of the infection. Clinical signs of haemonchosis became evident only in the low protein diet group. The infection was characterised by severe macrocytic anaemia, hypoproteinaemia, hypoalbuminaemia, reduced survival, high egg counts and a significantly greater worm burden. In the high protein diet group many lambs developed resistance to further infection in contrast to the low protein group in which no resistance developed. Live-weight gain was not affected by infection in the high protein diet group but decreased in the lambs given the low protein diet compared with uninfected controls. However, infection did not appear adversely to affect the digestive efficiency, nitrogen retention or iron absorption in either dietary group although loss of appetite occurred in the low protein group. Examination of a sample joint from the carcases showed infection was associated with a marked reduction in muscle mass in lambs given the low protein diet relative to the control animals.

The pathogenicity of haemonchosis in sheep and goats in Iraq: 1. Clinical, parasitological and haematological findings

The response of Awassi sheep and the local breed of Iraqi goats to primary infection with a prevalent trichostrongylid nematode, Haemonchus contortus, was compared by examining their worm burden and the pathogenic effects of the parasite on these hosts following experimental infection. The results showed that the goats had lower worm burdens and had suffered less severe clinical and haematological disturbances than the Awassi sheep. The worm counts in sheep were higher than in goats but the count of the mucosal phase of the larvae was higher in goats. These differences are possibly immunologic in origin though a genetic resistance may operate, primarily at the level of worm establishment. The pathophysiological changes are correlated with parasitological and clinical observations in the two host species.

Parasites as stressors: plasma cortisol responses of goats infected with the stomach worm Haemonchus contortus to exogenous corticotropin (ACTH)

Ten male, juvenile pigmy goats of similar age and weight were allocated randomly to two groups. Goats in one group were each inoculated with 20,000 infective larvae of Haemonchus contortus. The other group served as uninfected controls. Goats were housed together, and precautions were taken to avoid the creation of differential, between group, stressogenic circumstances. Body weights, nematode egg production, hematocrits, and clinical signs were monitored over a 61-day period following inoculation of larvae. On Days 59 and 61, adrenal response tests (ART) were conducted by measuring the levels of plasma cortisol before and 2 h after administration of porcine ACTH at the rate of 0.35 I.U. kg-1 body weight on Day 59 and 2.2 I.U. kg-1 on Day 61. Although the infections did not reduce body weights, they were 'heavy' on the basis of egg production, and led to significant reductions in packed erythrocyte volumes. There was no significant difference between the groups of goats in the responses to ART, indicating that the infections did not produce sufficient stress to reduce the ability of the adrenal cortex to respond to exogenous ACTH.

Changes in serum pepsinogen and haemoglobin concentrations in calves infected with Haemonchus contortus

In four calves given Haemonchus contortus larvae, the serum pepsinogen concentration rose quickly to reach a mean of 3.5 iu tyrosine on day 14 after infection. The mean concentration dropped to 1.8 iu tyrosine by day 23 and remained around 2.0 iu tyrosine until an anthelmintic was given on day 57, when concentrations returned to preinfection values.

The effect of dietary protein on the pathogenesis of acute ovine haemonchosis

Two experiments were conducted to examine the influence of dietary protein on parasite establishment and pathogenesis in Finn Dorset/Dorset Horn lambs infected with Haemonchus contortus. The lambs were introduced to high (169 g) or low (88 g crude protein (CP) kg-1 dry matter (DM)) protein diets at 3 months of age and infected 1 month later with 350 larvae kg-1 body weight (BW). Blood and faecal samples were collected for analysis and body weights recorded weekly. In the first experiment some of the infected lambs were killed 6 weeks after infection and the remainder 5 weeks later. In the second experiment all the infected lambs were killed 4 weeks after infection. The results showed that lambs on a low protein diet were less able to withstand the pathogenic effects of infection with 350 H. contortus larvae kg-1 BW than lambs given the higher protein diet. Thus mortality was greater in the low protein group and adverse clinical signs, such as inappetence, weight loss and oedema were observed more frequently. This group also had a more severe anaemia, hypoproteinaemia and hypoalbuminaemia than the high protein group. In contrast, faecal egg counts, total daily faecal egg output and worm burdens were similar in all groups of infected lambs, indicating that the diets did not influence parasite establishment.

The effect of dietary protein on the pathophysiology of acute ovine haemonchosis

An experiment was conducted to examine the effect of dietary protein on the pathophysiology of acute haemonchosis in Finn Dorset/Dorset Horn lambs. Erythrokinetic and metabolic studies using 51Cr-red cells, 59Fe-transferrin and 125I-albumin and digestive efficiency and nitrogen balance measurements were conducted between 19 and 39 days after infection. Identical radioisotopic and nutritional studies were conducted later on pair-fed control lambs. The results demonstrated that lambs on a low protein diet (88 g crude protein (CP) kg-1 dry matter (DM)) were less able to withstand the pathophysiological consequences of infection with 350 Haemonchus contortus larvae kg-1 body weight than lambs given a high protein (170 g CP kg-1 DM) diet, despite similar worm burdens. Erythrokinetic studies indicated that abomasal blood loss was similar in both groups of infected lambs, and circulating red cell volumes were reduced and plasma volumes were expanded to a similar degree in both groups. The majority of infected lambs in both dietary groups responded equally well to the gastric haemorrhage by increasing the rate of red cell production and their absorption of dietary iron was greater than in the control lambs. Albumin catabolism was increased in both groups of infected lambs, particularly in those given the low protein diet. Within each dietary group there were no differences in the digestibilities of the various proximate fractions of the experimental diets and no differences in the urinary or faecal nitrogen losses between infected lambs and their pair-fed controls. However, loss of appetite was a major feature of the disease, particularly in the lambs given the low protein diet and this feature appeared to be crucial in determining the ability of the infected sheep to withstand the pathophysiological effects of the parasite.

Influence of dietary protein on parasite establishment and pathogenesis in Finn Dorset and Scottish Blackface lambs given a single moderate infection of Haemonchus contortus

An experiment was conducted to examine the influence of dietary protein on parasite establishment and pathogenesis of Haemonchus contortus in lambs of two breeds. Finn Dorset and Scottish Blackface. The lambs were introduced to high protein (170 g crude protein (CP) kg-1 dry matter (DM) or low protein (88 g CP kg-1 DM) diets at three months old and infected one month later with 125 larvae (kg bodyweight)-1. Blood and faecal samples were collected for analysis and bodyweights recorded weekly. The lambs were killed 20 weeks after infection. A second experiment was conducted in Blackface lambs solely to determine the influence on parasite establishment of the high and low protein diets following infection with 125 larvae kg-1. These lambs were killed five or 14 weeks after infection. Results showed that in Scottish Blackface lambs dietary protein did not significantly influence the establishment of H contortus. However, in Finn Dorset lambs dietary protein may have influenced parasite establishment since lambs on the low protein diet had a higher faecal egg output four weeks after infection and more severe clinical signs than infected lambs of the same breed on a high protein diet.

Studies on the pathophysiology of chronic ovine haemonchosis in Merino and Scottish blackface lambs

An experiment was conducted to examine, under laboratory conditions, the pathophysiology of chronic ovine haemonchosis. In the present study, groups of Merino and Scottish Blackface lambs were maintained on a low plane of nutrition and infected with 50 Haemonchus contortus larvae/kg live weight. The parasitized lambs along with respective breed controls were examined over a 27-week period. In addition to the body weight, haematological and parasitological parameters, erythrokinetic, metabolic, digestibility and nitrogen balance studies were conducted in the early stages of the infection. The results demonstrated that a low level of infection with H. contortus in lambs on a poor plane of nutrition caused the development of a normochromic normocytic anaemia which was associated with a modest but significant increase in abomasal blood loss and slightly elevated erythropoiesis in both breeds relative to the controls. The level of anaemia, hypoproteinaemia and pathophysiological changes were more marked in the Merino lambs and they also had higher faecal egg counts than the Blackface lambs.

The prevalence and pathogenesis of naturally-occurring Haemonchus longistipes infection in Sudanese camels

Camel haemonchosis is prevalent in the Sudan, especially during the rainy season, with a decrease in prevalence in the dry season possibly due to delayed maturation of the worms. The naturally occurring disease in Sudanese camels is characterized by emaciation, anaemia, oedema of the lower parts of the limbs, eosinophilia, hypoproteinaemia, hypoalbuminaemia, hyperglobulinaemia and eosinophilia, as well as elevated blood urea concentrations.

The pathogenesis of experimental Haemonchus longistipes infection in camels

The pathogenesis and clinical signs of Haemonchus longistipes infection were studied in four experimentally infected camels two of which were adults and the other two were young. In the former animals, an acute infection developed, characterized by mucoid diarrhoea, anorexia, anaemia, loss of body weight, oedema of the lower parts of the limbs, general malaise and death at 8-10 weeks post-infection. In the two younger camels, a less dramatic disease was encountered with less severe symptoms and no oedema, but also terminating fatally at 19-20 weeks post-infection. Parasitological, haematological and biochemical parameters were determined during the course of the infection and were mostly comparable with those usually encountered in haemonchosis of other animals.

Erythrocyte potassium concentration: a simple parameter for erythropoiesis in sheep infected with Haemonchus contortus

A number of haematological parameters were monitored in eight-month-old Merino wethers, six infected with 10,000 Haemonchus contortus and 13 controls. Blood loss caused by infection was reflected in a decrease in packed cell volume (r = -0.78; P less than 0.001), and was correlated with faecal egg excretion (r = 0.89; P less than 0.001). Infected animals showed a decline of serum iron content and increased serum transferrin levels. Erythrocyte potassium concentration showed a high correlation with erythropoiesis as measured by iron59 clearance from blood (r = 0.79; P less than 0.001). As potassium assays are quick, inexpensive and samples can be stored for long periods, this parameter seems particularly useful in large experiments.

The pathogenesis of experimental Haemonchus longistipes infection in goats

Goats are highly susceptible to Haemonchus longistipes and could therefore serve as an inexpensive model to study camel haemonchosis. The course of the disease in goats is similar to that in camels and to H. contortus infection in sheep and goats. Unlike the age-dependency of camel haemonchosis, however, the severity of H. longistipes infection in goats is dose-dependent and varies from mild to hyperacute.

Quantitative studies of ovine haemonchosis. 2. Relationship between total worm counts of Haemonchus contortus, haemoglobin values and bodyweight

The relationships between Haemonchus contortus burdens, haemoglobin levels and bodyweight, were examined in 50 commercial Merino sheep, 9-18 months of age, in south-east Queensland where haemonchosis was endemic. Worm counts and haemoglobin levels were predictable (P less than 0.001, r = 0.68) from the equations log worm count = B.wt. X 0.06942 + log worm count X (-2.18896) + 12.51557. Bodyweight was not predictable from either worm counts or haemoglobin levels. Although bodyweight was represented in both equations, it was only a small and insignificant contributor. When haemoglobin levels became moderately depressed (less than 10.5 g%) or severely depressed (less than 8.0 g%), then the number of worms associated with these haemoglobin levels varied with the bodyweight of the sheep. For sheep up to 20 kg, 10.5 g% Hb was associated with 112 worms and 8 g% with 355 worms. However, 355 worms caused only moderate depression of Hb levels in sheep over 50 kg, and 1259 worms were required to cause severe depression (less than 8.0 g%) in sheep over 50 kg. Three sheep were found to be severely anaemic in the presence of less than 100 worms. It was postulated that additional factors of time and nutrition may have affected these sheep. The sheep were of low bodyweight, in poor condition (low fat score) and were subject to high stocking rates on long grass pastures and high rainfall in autumn. Other internal parasite species present were Nematodirus spp. and Trichostrongylus spp. However, their numbers were low (57 and 218 worms, respectively) and did not contribute to anaemia. The correlation between H. contortus and Nematodirus spp. was found to be negative but non-significant (r = -0.26, P less than 0.01), while the correlation between H. contortus and Trichostrongylus spp. was positive and significant (r = 0.38, P less than 0.01).

Self-curve and immunity following infection and reinfection in ovine haemonchosis

Egg expulsion and post mortem examination were used to compare self-cure and resistance to reinfection with Haemonchus contortus in female Merino sheep, AA and BB hemoglobin types. Animals were infected by 500 or 5000 larvae of H. contortus once, or several times, before being challenged by 500 (low dose) or 500 (high dose) larvae. In AA sheep infected once by 500 larvae self-cure was detected by a challenge of either 500 or 5000 larvae while in multi-infected sheep only a challenge of 5000 L, induced the self-cure. In BB sheep a mild self-cure was detected only by a challenge of 5000 larvae. In AA sheep receiving several infections, challenge by 500 larvae was not effective in producing resistance while 5000 L3 was effective in producing a state of resistance for up to 35 days post challenge. At post mortem examination, a strong state of resistance was evidenced in multi-infected animals by the low number of L4 and adults present in the abomasum up to the 35th day after challenge. In BB sheep no state of resistance was demonstrated by challenge with either 500 or 5000 L3, even in multi-infected animals.