[Control of bovine hypodermosis in Switzerland; looking back]. / Die erfolgreiche Bekämpfung der Hypodermose in der Schweiz: Ein Blick zurück.

For many years, hypodermosis control - which started in the 1920's - was unsatisfactory, partly due to a lack of efficacy or a too high toxicity of the available products. An improved control became possible with the introduction (1957) of the organophosphate Metrifonate (Neguvon®, Bayer AG). Subsequent large-scale campaigns according to the Federal Ordinance on epizootic diseases (1967) quite reduced hypodermosis in Switzerland. However, due to a limited use of the product (only young and alpine-grazing cattle were allowed to be treated, administratively indicated maximum dose, side-effects) and its incomplete efficacy, a full control was not possible. The decision to maintain hypodermosis as a "notifiable" disease then allowed further epidemiological studies. In 2000/2001 a concerted action in close cooperation with the cantonal veterinarians allowed a consequent and systematic treatment of all cattle in all endemic areas by the large-scale use of Eprinomectin (Eprinex®, Merial Inc.) for dairy cattle and of Ivermectin (Merial Inc.) as microdose "off-label" for young cattle has led to a rapid and sustainable success.

[Recent data on the treatment of bovine hypodermyiasis using metrifonate (Neguvon) and ivermectin (Ivomec) in microdoses]. / Données récentes sur le traitement de l'hypodermose bovine au moyen de métrifonate (Neguvon) et d'ivermectine (Ivomec) en microdoses.

Large scale preventive treatments against bovine hypodermosis have been performed in the Canton of Grisons and in different Jura areas. Either Metrifonate (Neguvon 10% spot-on, Bayer AG) or Ivermectin "microdoses" (i.e. 0.1 ml Ivomec ad. inj-MSD AGVET-per animal) have been applied. The treatment of dairy cows with Neguvon at the then recommended dose (24 ml/animal) showed a low efficacy of 80%, without any correlation to the date of treatment. An increase of the dose to 36 ml/animal revealed an efficacy of 93%, while a weight-dependent dose of 6 ml/100 kg body weight reduced the warble infestation by 97.3% without any drug-related side-effects. The few observed side-effects-salivation and mild meteorism--are likely to be due to the destruction of Hypoderma lineatum larvae in the gullet of treated cows. No case of abortion was reported. The Ivomec--"microdose" applied to young animals or dry cows showed an efficacy > 99.8%. The available drugs would thus allow a quick and efficacious control of bovine hypodermosis, provided they would be used systematically and at an appropriate dose in endemic areas.

[Epidemiology of bovine hypodermyiasis in canton Vaud: comparison of two methods of mapping the infestation with a view to strategic treatment]. / Epidémiologie de l'hypodermose bovine dans le Canton de Vaud: comparaison de deux méthodes de cartographie de l'infestation en vue d'un traitement stratégique.

The geographic distribution of bovine hypodermyiasis in the canton Vaud/Switzerland has been investigated in two ways: By direct examination of the animals by the livestock officers at the 1993 annual census and by ELISA on bulk milk sampled in January 1994. The efficacy of the two methods is compared and the distribution of hypodermyiasis presented on a map. The serological analyses have revealed a highly satisfactory degree of sensitivity and specificity (92.1% and 98.1%, resp.). The epidemiological interpretation however, is rather difficult, partly because quite often the animals are not infested on their farms but rather while being on alpine pastures. A monitoring of the herds with a view to an efficient control of hypodermyiasis could thus in a first instance be based on the indications provided by the livestock officers, whereas a serological monitoring in a second place would allow to detect the last and remaining foci of infestation.

Cellular reactions in the small intestine of rats after infection with Fasciola hepatica.

Groups of five rats each were infected with metacercariae of Fasciola hepatica according to two experimental procedures. In the first experiment, they received 20 metacercariae 0, 1, 2 or 3 times at intervals of 4 weeks. In the second, both the inoculation dose and the interval between doses were varied. After the animals had been killed, the small intestine was prepared for histology and tissue sections were stained for the detection and quantification of mucosal mast cells (MMCs), eosinophils and goblet cells. The density of eosinophils and MMCs increased significantly with each reinfection in the first experiment; in the second, the MMC reaction reached a peak at 4 weeks post-infection (p.i.), whereas the eosinophils peaked at 4 and 17 weeks p.i. In addition, the reaction of these cells depended on the infectious dose. In both experiments, goblet cells reacted only weakly. These findings thus clearly reflect a considerable intestinal response against migrating juvenile F. hepatica. The pattern of these defence reactions in the small intestine suggests some similarities with the mechanisms of antibody-dependent cell-mediated cytotoxicity that have been shown to take place during Schistosoma mansoni reinfection.

[Intestinal cellular reaction of cattle after infection by Fasciola hepatica]. / Réactions cellulaires intestinales du bovin après infection par Fasciola hepatica.

Defence reactions of cattle against Fasciola hepatica take place not only in the liver but also on a prehepatic level. The aim of the present experiments is to identify and quantify the cellular response in the small intestine. Five groups of two bulls (Simmental x Red Holstein, 6 months old) were infected by oesophageal probe with metacercariae of F. hepatica (MC) according to two experimental procedures. Two groups of bulls served as controls. In the first experiment both infected groups received 1000 MC once or twice at an interval of five weeks. The intestinal tissue was taken before infection and 5, 10 and 19 weeks p.i., respectively 5 and 14 weeks p. reinf. (p.ri.). In the second experiment, three infected groups received 400, 2 x 400 MC (at an interval of five weeks) and 800 MC respectively. Biopsies were taken one week ante infectionem, 6, 11 and 19 weeks p.i., respectively 1, 6 and 14 weeks post reinfectionem (p. ri.). The biopsies of the small intestine were prepared for histology and the tissue sections stained as follows: Astra blue for mucosal mast cells (MMC), Lendrum for eosinophils (EOS) and Periodic Acid Schiff (PAS) for goblet cells (GC). The density of the three cell populations in the mucosa was determined microscopically and quantified. In both experiments the density of the MMC and EOS increased with each reinfection and depended on the infectious dose. There was no significant variation of the GC-numbers. The described intestinal cellular reactions suggest a participation of the small intestinal wall in the immunity against the common liver fluke.