Stomach Worm Research Articles

Scanning Electron Microscopy of the Sheathed Infective Larva and Parasitic Third-Stage Larva of Haemonchus contortus (Nematoda: Trichostrongyloidea)

Scanning electron microscopy was used to describe the infective and parasitic third-stage larvae of Haemonchus contortus, the large stomach worm of ruminants. Infective larvae are ensheathed in the cuticle of the second stage, so the descriptions are of the second- and third-stage cuticles. Both larval stages had an inner circle of 6 labial papillae, an outer circle of 6 labial papillae and 4 somatic papillae, and lateral amphidial pits. Infective larvae (cuticle of the second stage) had the 6 internal labial papillae on prominent bluntly rectangular lappets in a star-shaped arrangement around a large triradiate mouth, small triangular or round amphidial pits, flattened ribbonlike lateral alae, and phasmidial apertures opening on the ventral surface of the lateral alae. Parasitic third-stage larvae had the 6 internal labial papillae on small elevations without lappets around a small mouth; large, oval amphidial pits; ribbonlike lateral alae for most of their length, but with the anterior 30-40 microns of the alae cordlike; and phasmidial apertures on the body cuticle ventral to the lateral alae.

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.

The seasonal occurrence of Trilocularia acanthiaevulgaris (Cestoda: Tetraphyllidea) from spiny dogfish in the Irish Sea.

Trilocularia acanthiaevulgaris occurs in the stomach and spiral valve of the spiny dogfish. Statistical analyses show that the stomach and spiral valve worms of male fish and the stomach worms of female fish exhibit seasonal trends in prevalence and mean worm burden, with peaks occurring in May, June and July of each year. Spiral valve worms of female fish do not show this trend. Calculation of the product-moment correlation coefficient shows that the peak in the number of stomach worms occurs approximately 1 month before that of spiral valve worms in male fish. Strobilization of the adult spiral valve worms and development of the resulting free proglottides is also seasonal, and takes place in June/July in both sexes. Seasonal trends in prevalence, mean worm burden and maturation of T. acanthiaevulgaris may be related to water temperature, and the cyclical changes in levels of reproductive hormones and thyroid activity associated with migration and mating of spiny dogfish. It is suggested that the availability of infected intermediate hosts and diet of the dogfish may also be important in explaining the seasonality of infection.

Other Parasites: Recent Advances

This article briefly reviews new information on trichostrongylid stomach worms, spirurid stomach worms, tapeworms, threadworms, pinworms, intestinal protozoa, lungworms, eye worms, and numerous other aberrant parasites as it relates to prevalence, pathogenesis of diseases, and treatments.

The Significance and Control of Stomach Worms in British Cattle

Stomach worms are widely prevalent in cattle and are a serious cause of death and lost production. Although they can be controlled either by chemotherapy or by systems of pasture management – or a combination of both – success depends upon knowledge of the parasite's life cycle.

Arrested development of the rabbit stomach worm Obeliscoides cuniculi: Resumption of development of arrested larvae throughout the course of a single infection

Arrested development of the rabbit stomach worm Obeliscoides cuniculi: resumption of development of arrested larvae throughout the course of a single infection. International Journal for Parasitology 16: 47–54. Twenty rabbits were inoculated once with cold treated L3s of Obeliscoides cuniculi with a high propensity for arrest and killed in pairs at intervals over 234 days post-infection. An exponential decline in numbers of adult worms and arrested larvae was observed. Arrested larvae resumed development at a rate seven times greater than adults were lost and appeared to replenish the adult population. More male than female arrested larvae were intially established in rabbits but males resumed development at a greater rate than females. Egg and larval production were correlated with the number of female worms present at any one time. In a subsidiary study, arrested larvae were recovered from one rabbit and transferred sequentially through two further rabbits. These larvae resumed development at the same rate as larvae in the 20 rabbits. Both studies suggest that resumption of development is an intrinsic characteristic of the larvae themselves and may be genetically controlled.

Arrested development of the rabbit stomach worm Obeliscoides cuniculi: Varied responses to cold treatment by the offspring produced throughout the course of a single infection

Arrested development of the rabbit stomach worm Obeliscoides cuniculi: varied responses to cold treatment by the offspring produced throughout the course of a single infection. International Journal for Parasitology 16: 55–61. In an experimental model, rabbits were inoculated with cold treated L3s (parental generation) to establish infections with a high proportion of arrested larvae. Over 234 days, ten batches of L3s (offspring) were derived sequentially from ten pairs of rabbits. Samples of L3s (offspring) were cold treated for various periods (13–74 days) and inoculated into test-rabbits to determine cold treatment time for maximum arrest (CTTMA). As parental infections proceeded, the CTTMA varied from batch to batch of offspring. Their propensity for arrest also varied, but no correlation was found between duration of infection by parents and propensity for arrest by offspring. Three additional rabbits were treated early in their infections with thiabendazole. Offspring larvae subsequently derived from these rabbits exhibited significantly more arrest than those from untreated hosts. The model shows that, in natural infections, overwintering arrested larvae could transmit genes for arrest to their spring progeny but that such genes would remain unexpressed until acted on by the correct environmental stimulus.

Helminths of the camel: a review.

Abstract Conditions under which camels are usually kept are not conducive to parasite transmission; in spite of this a large number of helminth parasites are known to occur in the camel. Most of these infections do not precipitate frank clinical disease; some species, however, are important as aetiological agents of clinical conditions which are often the result of mixed infections. These include the camel stomach worm Haemonchus longistipes. This helminth, either alone or in mixed infections with Trichostrongylus spp., may cause a debilitating and sometimes fatal condition. Other common helminth infections of the camel include onchocerciasis caused by Onchocerca fasciata, Dipetalonema evansi infection, Fasciola hepatica, F. gigantica, Stilezia vittata, Moniezia expansa and larval Echinococcus granulosus. Information available about helminths of the camel is presented and discussed.

Arrested development of the rabbit stomach worm Obeliscoides cuniculi: Manipulation of the ability to arrest through processes of selection

Through a process of selection in an isolate of O. cuniculi, the propensity for arrested development in response to cold treatment was increased from 15 to over 90% in five generations. In subsequent generations, the propensity for arrest remained high so long as selection pressure was maintained. The selected high arresting isolate exhibited a corresponding increase in ability to arrest without prior cold treatment of infective larvae. In the absence of selection for arrest, this isolate reverted to one with a lower propensity for arrest. These results indicate that arrested development has a genetic basis. A hypothesis was developed which proposed that continuous variation in the rate of development is controlled by polygenes and that a worm will exhibit arrested developmet if its genotype has an enrichment of alleles for slow growth at the various polygenic loci.

The effects of single and multiple doses of thiabendazole on growing and arrested stages of the rabbit stomach worm Obeliscoides cuniculi

Preliminary observations, using 5 rabbits carrying long-standing infections, indicated that single doses of thiabendazole were effective against adult O. cuniculi and that repeated doses may have had some effect on arrested larvae. A multiple dosing regime, consisting of 1 dose at 110 mg kg −1 body weight followed by 8 doses at 70 mg kg −1 body weight at 4-h intervals, was successful in removing 99.12% of developing worms and 86.04% of arrested larvae.

Experimental infection of sheep by the camel stomach worm, Haemonchus longistipes

An attempt has been made to infect sheep by Haemonchus longistipes with the objective of developing a relatively cheap and manageable model of camel haemonchosis. A large proportion of inoculated animals ( 28 34 ) developed patent infections; the prepatent period was short, lasting for 3 to 4 weeks in the majority of infected animals. Worm burdens were low and so was the total egg output. Most of the recovered worms were reduced in size.

A comparative study ofTrilocularia acanthiaevulgaris Olsson 1867 (Cestoda, Tetraphyllidea) from the stomach and spiral valve of the spiny dogfish

Differences in the internal anatomy and ultrastructure ofTrilocularia acanthiaevulgaris from the stomach and spiral valve of the spiny dogfish are described with the aid of electron microscopy and light microscope histochemistry. Worms from the stomach rarely exceed 7 mm in length and do not exhibit signs of segmentation. In contrast, spiral valve worms are segmented, reach a length of some 30 mm and release free proglottides which mature whilst detached from the strobila. Numerous calcareous corpuscles and large glycogen-filled vacuolations occur throughout the body of stomach worms, but are almost totally absent from spiral valve worms. The neck region of spiral valve worms is packed with many germinative cells. The distal tegumental cytoplasm of the stomach worm contains many electron-lucid vesicles, mitochondria and forming microtriches. Microtriches on the tegumental surface are scant, and those present are directed posteriorly. The distal tegumental cytoplasm of the spiral valve worm contains few electron-lucid vesicles and mitochondria but has many dumb-bell-shaped vesicles. Microtriches are longer and more numerous than those of stomach worms. The differences suggest thatT. acanthiaevulgaris worms from the stomach are juveniles which migrate to the spiral valve where they develop into the adult.

Epidemiological observations on stomach worms of horses in Morocco

Six to nine horses per month (total of 94 in a year) were examined for stomach worms in the Settat region of Morocco. All the animals were infected by at least one helminth species. Habronema muscae occurred in 95.8%, H. majus in 75.6% and Trichostrongylus axei in 80.9% of horses. Polyparasitism was observed in 93.6% of horses. Both for Habronema sp. and T. axei the peak worm burden was observed in November and minimum in June. The infection pattern of Habronema spp. was directly related to the period of activity of fly vectors.

In vitro cultivation of Ostertagia ostertagi, the medium stomach worm of cattle. II. Effect of insect-growth-disrupting amines and amides on development

Thirteen secondary and tertiary amides and amines that disrupt growth and development in certain insects were tested at concentrations of 0.25–5.0 p.p.m. for their effects on development of Ostertagia ostertagi, from infective larvae to egg-laying adults, in a two-step roller culture system. These compounds did not affect exsheathment of infective larvae. However, some of these compounds inhibited development or killed 100% of the exsheathed larvae at concentrations of 1.0–2.5 p.p.m. Minimum inhibitive concentrations of several of the amines and amides affected the nematodes in one or more of the following ways: decreased motility or paralysis; reduced survival; delayed or blocked third or fourth ecdysis; lowered yields of advanced stages; decreased production of fertile and non-fertile eggs. The results also indicated that, as in insects, these chemicals exerted their lethal effects against O. ostertagi at the time of molt.

Antigens of Hyostrongylus rubidus, the red stomach worm of pigs. Analyses by means of passive haemagglutination and immediate hypersensitivity tests

Antigens were prepared from different stages of worm development and adult worm antigens were fractionated by ion exchange and exclusion chromatography. The antigens, or fractions of them, were assessed for their activity in passive haemagglutination reactions or intradermal tests. The results of the passive haemagglutination reactions indicated that circulating agglutinins were more readily detected when adult stage specific antigens were used. Antigen prepared from worms isolated when the population was declining was less sensitive. Fractions of adult worm antigen did not confer greater sensitivity than the whole worm extract.

Helminth Parasites of Grey Kangaroos, Macropus Giganteus Shaw and M. Fuliginosus (Desmarest), in Eastern Australia.

In a survey in eastern Australia, 104 Macropus giganteus and 40 M. fuliginosus were examined at autopsy for helminths. 32 species of nematodes (28 strongyloids 2 oxyuroids and 2 filarioids) and 6 species of anoplocephalid cestodes were found. Most species occurred in both hosts. The most prevalent and numerous nematode in both species was Rugopharynx australis which reached numbers up to 290 000 in M. fuliginosus. Pharyngostrongylus kappa was also common and widespread but occurred only in M. giganteus. The most striking stomach worms were Labiostrongylus kungi and L. bipapillosus which occurred in both hosts. Various Cloacina spp. were found, some specific to one host, others occurring in both. Other species of stomach nematodes were relatively uncommon. The parasites of the small intestine were 2 species of Globocephaloides, 2 of Triplotaenia and 2 of Progamotaenia. 2 other species of the latter genus occurred in the bile ducts. The large intestine harboured 6 species of nematodes, including Macropoxyuris spp. which were very numerous in both hosts. The 2 species of filariids found (both in Macropus giganteus) were Breinlia mundayi (new host record) in the abdominal cavity and Dirofilaria roemeri in the connective tissues.

In vitro Cultivation of Ostertagia ostertagi, the Medium Stomach Worm of Cattle. I. Development from Infective Larvae to Egg-Laying Adults

When a 70-min exsheathing process and two-step roller culture system were used, infective larvae of Ostertagia ostertagi developed in large numbers to mature adult males and females in 28 and 29 days, respectively. Females laid fertile eggs in the 2- to 16-cell stages from day 34 on. Some of the expelled eggs developed to the morula stage, in the culture fluid, by day 52. Yields of mature adults and eggs were best when cultures were started with 100,000 larvae in 100 ml of medium. The optimal culture system produced from 20% to 35% mature adults, from days 28 through 52.

The anthelmintic efficacy of cambendazole in horses

Summary The anthelmintic activity of cambendazole 31% paste was evaluated in a controlled trial against naturally acquired gastro-intestinal parasites of the horse. Four groups of five adult horses were treated at dose rates of 0, 15, 20 and 25 mg/kg. The three dose levels of cambendazole tested were efficacious against the large strongyles Strongylus edentatus and S. vulgaris, the stomach worm Trichostrongylus axei, the pinworms Oxyuris equi and Probstmayria vivipara and all the species of small strongyles present. No efficacy was demonstrated against the tapeworm Anoplocephala perfoliata or the horse bots Gasterophilus intestinalis or G. nasalis

The immune response of pigs to infection with the stomach worm Hyostrongylus rubidus (Hassall and Stiles, 1892) : I. Antibody production in response to primary infection

Pigs infected with single doses of third stage Hyostrongylus rubidus larvae showed a detectable circulating agglutinin response as early as 2 days post infection. Although titres fluctuated considerably before patency, a trend in antibody production could be detected which followed the active development and growth of larvae in the gastric mucosa. At patency, titres showed a large, rapid increase followed by an equally dramatic decrease, after which titres remained stable or increased gradually. Pigs infected with adult worms did not show a detectable agglutinin response until 7 days post infection or later. Little fluctuation in titre was observed. Response variation between different levels of infection was great as was the variation between different litters subjected to the same infection regime. No statistical difference could be found in total antibody production between pigs infected with different larval numbers at any time during the duration of the trial.

The immune response of pigs to infection with the stomach worm Hyostrongylus rubidus (Hassall and Stiles, 1892) : II. Multiple infections and reinfections in growing pigs and sows

Pigs given multiple infections of third stage Hyostrongylus ribidus larvae over a 10-day period produced detectable circulating agglutinins 2–3 days after the initial infection. Titres were neither higher nor more prolonged than those of pigs which received a single infection of larvae, although fluctuations in titres over a 30-day period were more marked. Pigs reinfected with a single dose of third stage larvae, however, showed a rapid initial decline in titre followed by a gradual increase to a level higher than that detected at primary infection. Biological manifestations of immunity such as a decreased parasite egg output and increased prepatent period were also seen. The host reaction to reinfection is regarded as an anamnestic response.