Morphological, histochemical, and biochemical studies on the gut of Haemonchus contortus Rud., 1803)

Haemonchus in India

Haemonchosis is an acute problem in India. Three species of Haemonchus occur. These are H. contortus (Rudolphi, 1803) which occurs in sheep, goat, cattle, buffalo and other ruminants; H. longistipes Railliet && Henry, 1909 occurring in camels and H. similis Travassos, 1941 in cattle. Seasonal fluctuation of H. contortus occurs, with infection being more frequent in autumn ≻ summer ≻ winter ≻ spring, and infection in sheep and goats has been reported to be 100 %. Various aspects of haemonchosis have been investigated. However, the fundamental and the most challenging areas in Haemonchus research remain almost untouched. In order to forecast the development of haemonchosis, epidemiological studies should be undertaken on the prevalence, distribution and seasonal incidence of the worm to understand the effects of climatological factors like rainfall, humidity and temperature. The sparse and inadequate studies of metabolism need to be extended to other areas of Haemonchus biochemistry to provide additional possibilities for exploration of hostparasite differences. Clinical haemonchosis in sheep, goats and other ruminants should be studied in order to calculate losses caused by mortality and the cost of anthelmintic medication. Most anthelmintics are expensive, and are not easily available to our farming community, therefore a search for many more indigenous anthelmintics (such as Wopell, Krimos, Sonex etc) must be made. Detailed knowledge of the mode of action and route of entry of anthelmintics at the molecular level could also be beneficial, particularly when the strains of H, contortus have been identified as resistant to some anthelmintics. The prospects of producing a vaccine against H. contortus should be explored. Attempts in this field have already been made by overseas workers (see Clegg && Smith, 1978) and in India too, work has been undertaken at Kerala (Sathianesan, personal communication). Therefore, because of its economic importance and wide distribution, H. contortus provides fascinating research material particularly in the warmer regions of the world.

Cholinesterase and phosphatase activities in adults and infective-stage larvae of levamisole-resistant and levamisole-susceptible isolates of Haemonchus contortus

Cholinesterase (ChE) and acid phosphatase (AP) activities, but not alkaline phosphatase activities, were detected in cytosolic and membrane-bound fractions of adult and infective-stage larvae of levamisole-resistant and levamisole-susceptible Haemonchus contortus. In contrast to other gastrointestinal nematodes, the ChE activity was higher in L3 than in adults and, in both cases, was mainly associated with membranes. ChE activity was inhibited by Triton X-100 and was only detected in membrane-bound fractions when the detergent was removed. Differences between resistant and susceptible L3 were observed in the response to inhibitors (cytosolic fraction) and in the enzymatic content (membrane-bound fraction). Phosphatase activity was detected at acidic pH in all fractions, being higher in the adult than in the L3 stage. In the former, most of the enzyme was localized in the membrane-bound fractions, whereas in the latter it was mainly in cytosolic fractions. This difference could be correlated with the activity in the gut. In inhibition assays, a difference between cytosolic fractions from resistant and susceptible adults was observed in their response to 1 mmol/L tartaric acid.

Studies on kinetic properties of non-specific phosphomonoesterases in the sheep nematode, Bunostomum trigonocephalum Rudolphi, 1808

The maximum activity (Vmax) of acid phosphomonoesterase (E.C.3.1.3.2.) at pH 5.5 and 37 degrees C was found to be 2.68 +/- 0.25 and 3.85 +/- 0.24 mu moles phenol mg protein-1 min-1 in male and female Bunostomum trigonocephalum, respectively. The Vmax of alkaline phosphomonoesterase (E.C.3.1.3.1) at pH 10.0 and 37 degrees C was 0.75 +/- 0.04 and 1.15 +/- 0.05 mu moles phenol mg protein-1 min-1 in male and female B. trigonocephalum, respectively. The Michaelis constant (Km) values were 10.25 mM and 11.76 mM for acid and 8.69 mM and 9.09 mM for alkaline phosphomonoesterase in male and female worms, respectively. Enzymal activities were optimum at 7.0 and 9.0% enzyme concentrations, at incubation periods of 60 and 20 min and at temperatures of 50 and 45 degrees C for acid and alkaline phosphomonoesterases, respectively. Dialysis in distilled water decreased the activity of both enzymes, while only acid phosphomonoesterase activity increased in citrate buffer (pH 5.5) and alkaline phosphomonoesterase activity in carbonate buffer (pH 10.0).

A comparison of the sites of acid phosphatase activity in an adult filaria, Setaria sp. and in some gastro-intestinal nematodes

The histochemical localization of acid phosphatase in an adult filaria, Setaria sp. obtained from the peritoneal cavity of a cow was closely examined and compared with that of adult nematodes parasitic in the host alimentary canal; special attention was paid to the intestine and body wall of the parasites. Setaria sp. was found to show high acid phosphatase activity in the interchordal hypodermis of the body wall and uterine microfilariae, and similar activity is suspected to occur in the cuticle. The intestine of this nematode exhibited very low, if any, activity. In contrast, nematodes parasitic on the alimentary canal, such as Toxocara cati, T. canis, Physaloptera sp. and Ancylostoma caninum, showed no activity in the body wall and very high activity in the luminal surface of their intestine. The possible function of the abundant acid phosphatase in the body wall of this filaria is discussed.