Treatment vs non-treatment of helminth infections in cattle: defining the threshold.

In this paper the different options for the diagnosis of gastrointestinal nematode infections are discussed. Diagnostic tests have a role in confirming the clinical diagnosis of parasitic gastroenteritis, but are more important for herd health monitoring of nematode infections, in particular for cattle. Therefore, emphasis is placed on discussing the available diagnostic parameters on their usefulness for that purpose. For clinical diagnosis the clinical signs, combined with the history of the animals is usually sufficient and a laboratory confirmation is not required. Faecal egg counts are, with two exceptions, not suitable for confirmation of the clinical diagnosis, because correlation between faecal egg counts and infection levels is usually low. These exceptions are the diagnosis of haemonchosis in small ruminants and the detection of anthelmintic resistance. This also limits the value of DNA-based tests of faecal material; even quantitative tests of nematode species specific DNA will have little value for diagnosis and monitoring. Pasture larval counts and worm counts are useful parameters for basic epidemiological studies on nematode infections. However, they are too laborious to be used for either routine diagnosis or monitoring. Blood parameters, such as gastrin and pepsinogen and serology are valuable tools for diagnosis. Pepsinogen and ELISAs based on recombinant proteins show most promise as parameters for herd health monitoring. However, extensive epidemiological studies are still needed before these parameters can be implemented in routine herd health monitoring schemes for parasitic gastroenteritis.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0031182099005752

Value of present diagnostic methods for gastrointestinal nematode infections in ruminants.

Pathophysiology of infection with gastrointestinal nematodes in domestic ruminants: recent developments.

The anthelmintic efficacy of five plant products against gastrointestinal trichostrongylids in artificially infected lambs.

https://orgprints.org/6994/1/vetparasitol2005sainfoin.pdf

Effects of the repeated distribution of sainfoin hay on the resistance and the resilience of goats naturally infected with gastrointestinal nematodes.

Blood pepsinogen concentrations in cattle were determined, using a simple, direct method based on the hydrolysing effect of serum on buffered bovine albumin substrate (2 g/dl). The amount of tyrosine released was measured at 680 nm, using the Folin and Ciocalteu's colorimetric method. To ensure an optimal digestion in vitro, a glycine-hydrochloric acid buffer (0.1M) was evaluated at various pH. Serum samples with medium (2,591 mU of tyrosine) and high (6,222 mU of tyrosine) pepsinogen concentrations had the highest proteolytic activity at pH 2.5. Substituting albumin by hemoglobin substrate resulted in almost double the amount of hydrolyzed products. For preparation of standard pepsin or pepsinogen curves, the incorporation of serum (activated or inactivated) diminished the tyrosine released to only half the amount obtained without serum. The use of serum or plasma did not significantly affect the results of the test, nor did prolonged storage at -70 C result in marked differences in the results.

Evaluation of a simplified blood pepsinogen assay

Summary

Gastrin values were evaluated in 130 parasite naive calves, in 61 first season grazing calves during six field trials and in 8 experimentally infected adult immune cows. The gastrin values were linked to pepsinogen levels and daily weight gain. Also the influence of an anthelmintic treatment on pepsinogen and gastrin values was assessed during a clinical outbreak of ostertagiosis in a group of first season grazing calves. Mean gastrin levels in parasite naive calves were 106 pg/ml. Results show that a group mean of 400 pg/ml gastrin in first season grazing calves indicates a reduced daily weight gain but with no obvious clinical signs. During clinical outbreaks mean gastrin levels frequently reached 1,000 pg/ml with a severe weight loss and a mean pepsinogen level of 5,000 mU tyr. The serum gastrin concentration was strongly reduced 4 days post treatment. No gastrin response was noted following an Ostertagia challenge in adult immune cows.



The value of gastrin as a diagnostic aid for ostertagiosis is discussed in relation to pepsinogen, the adult worm burden, larval inhibition and the technique involved in assessing gastrin.

Diagnostic value of gastrin for clinical bovine ostertagiosis

A field experiment is described which evaluates the use of an experimental albendazole pulse release bolus (E-bolus) on gastrointestinal parasitism. The bolus was administered at turnout to 9 first-season grazing calves and 9 animals were kept as controls on a separate pasture. Dry summer observed. The E-bolus introduced at the start of the grazing season provided moderate control of gastrointestinal parasitism. The beneficial effect of the treatment was demonstrated by lower strongyle egg counts and significant differences in ELISA extinctions for Ostertagia, Cooperia and Dictyocaulus. However pepsinogen values were elevated in the bolus-treated group, probably because of the long interval (31 days) between the pulsed treatments. Although not significant there was a trend for the bolus-treated group to gain more weight than the controls.

Field evaluation of an experimental albendazole pulse release bolus in the control of parasitic gastroenteritis in first-season grazing calves.

Subclinical parasitism in calves: biochemical and serological evaluation of preventive treatment against gastroenteritis and husk.

During our study on the evaluation of treatment with cambendazole (Ascapilla, Chevita) for Capillaria obsignata in pigeons, we observed that many of the eggs were abnormally shaped following administration of the drug in the prepatent period. Pigeons (N=24) were infected with 6,000 embryonated C. obsignata eggs, and each pigeon was treated twice with 30 mg cambendazole with a 1-week interval. The first treatment was given on the following days postinfection (d.p.i.): 3, 6, 9, 12, 15, 18, or 21. Almost all pigeons excreted C. obsignata eggs from 21 d.p.i, onwards; most eggs were of normal size (52.1_+5.5 gm based on 1000 measurements), but some were abnormally long, i.e., longer than 60 ~tm (72.5 ___ 5.9 gm based on 117 measurements) (Fig. 1). To understand more about the excretion of abnormal eggs, two surveys were done. Pigeons ( N = 6) infected with 6000 C. obsignata eggs were treated on day 3 postinfection (p.i.) with 30 mg cambendazole. They excreted eggs 21 d.p.i. ; 13%-26% were longer than 60 gm, with a maximum length of 106 gm. Eggs were cultured; 85% of the normal eggs embryonated, in contrast to only 37% of the eggs longer than 60 gm (Fig. 2). In a second trial, 4 pigeons were infected with a mixture of normal and abnormal eggs (44/56). During the first days of the patent period, some abnormal eggs were seen. The pigeons with worms producing abnormal eggs were killed, and the female worms ( N = 30) were examined. The following results were obtained: 22 females contained normal eggs, with a mean of 155 eggs, and 4 female worms contained only abnormal eggs (average length of 75 gm) ; the mean was 29. In 4 female worms, both normal and abnormal eggs were observed in utero (about 67% were normal), with an average of 43 eggs (Fig. 3). Changes in nematode egg morphology after administration of a benzimidazole have been reported several times. Following the administration of mebendazole to 24 humans for the treatment of Trichuris trichiura infections, the eggs of this worm were abnormal in size, shape, and color (Wagner et al. 1974). After oral treatment of T. muris infected mice with 500 mg/kg febantel, the majority of eggs excreted beginning 31 h after treatment did not develop into larvae (Thomas 1979). A more pronounced ovicidal effect was shown in Haemonchus contortus after treatment of sheep with 2.5 mg/kg febantel (Thomas 1979). Similarly atypical eggs of H. contortus, Ostertagia circumcincta, and Trichostrongylus colubriformis were detected after treatment with fenbendazole (Kirsch and Schleich 1982). On the other hand, Jansen (1984) has observed the production by female Trichuris worms of two different-sized eggs, without a history of treatment. From the evidence reported, it appears that benzimidazoles have a pronounced ovicidal activity in female trichostrongylids, whereas in Trichuroidae (Trichuris, Capillaria), eggs are often viable but abnormal in size, shape, and color. It seems that the drug acts on the ovary during treatment.

P. Berghen

Papers

Evaluation of a simplified blood pepsinogen assay

Diagnostic value of gastrin for clinical bovine ostertagiosis

Field evaluation of an experimental albendazole pulse release bolus in the control of parasitic gastroenteritis in first-season grazing calves.

Subclinical parasitism in calves: biochemical and serological evaluation of preventive treatment against gastroenteritis and husk.

Morphological changes in Capillaria obsignata (Nematoda: Trichuridae) eggs after treatment with camhendazole