Selective deworming

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Selective deworming is a method of combating parasitic nematodes of ruminants and equidae that was originally designed for humans and is now used worldwide. In the sense of evidence-based medicine, a remedy against worm infestation (or anthelmintic ) should only be given if certain criteria are met by the individual animal. In ruminants, these include clinical symptoms or the results of clinical examinations (e.g. coloration of the conjunctiva) or the results of fecal examinations. For equidae, the criterion at the moment is the egg excretion of the individual horse. If this exceeds a threshold value defined for the worm species in question, it is dewormed. So far, rigid, periodic treatment intervals have been common, so-called strategic deworming. The treatments were carried out without prior diagnosis (which worm species is present in the herd) and mostly without monitoring the success of the treatment (for example: treatment every eight weeks). The reason for the selective deworming is the development of resistance among the parasites, which means that many of the agents used only have a limited effect.

background

Traditionally, the most important parasitic nematodes of the horse are the large species of the genus Strongylus , primarily the horse palmetto worm Strongylus vulgaris , more rarely Strongylus edentatus and Strongylus equinus . Until the 1960s, these were responsible for the majority of colic in horses , not infrequently also for deaths. In the 1960s newly developed antihelmithics, especially the benzimidazole class of active ingredients , led to a dramatic reduction in these previously feared diseases. The interval dose program was developed as a treatment method, in which frequent repetitive treatments prevented the development of the nematode eggs and thus interrupted the chain of infection.

Since then, however, there has been a steep increase in infestation by smaller strongyles, especially the tribe Cyathostominea, which are increasingly resistant to all commercially available antihelmithics. The development of resistance is also expected in the case of agents such as ivermectin , which are still effective ; sooner or later it is scientifically unavoidable if the parasites are constantly exposed to more or less low-dose active ingredient concentrations. There are currently no new classes of active ingredients in sight. Since the beginning of the 1990s there has therefore been the opinion among parasitologists that constant, frequent (e.g. 4 times a year) de-worming treatment of horses may not be the right approach.

execution

On the basis of the excreted eggs, the horses are checked in advance to determine whether deworming is even necessary. If the infestation is below the treatment threshold, they are examined again after a defined time interval. Should a horse have a health-impairing infestation with a certain endoparasite at the time of the examination, it is treated with a defined active ingredient (dewormed) and 14 days after the treatment it is checked again by a special excrement sample examination whether the agent used was also effective.

Selective deworming has been a legal requirement in Denmark since 1999. As a result, similar laws were introduced in Sweden, the Netherlands, Finland and Italy.

swell

Individual evidence

  1. ↑ Anderson RM, May RM: Population dynamics of human helminth infections: control by chemotherapy . In: Nature . tape 297 , 1982, pp. 557-63 .
  2. ↑ J Bollinger, H Hertzberg, M Hässig, G Knubben-Schweizer: 'Targeted' and 'targeted selective treatments' in goats: Evaluation of several decision criteria and development of a practical decision key . In: Switzerland Arch Tierheilkd . tape 158 , no. 8 , p. 557-564 , doi : 10.17236 / sat00077 ( gstsvs.ch [accessed December 27, 2016]).
  3. ↑ Dr Anne Becher: Statement of a faecal sample on a horse. Retrieved December 27, 2016 .
  4. ↑ Martin K. Nielsen, DVM, Ph.D., Dipl. EVPC, Linda Mittel, MSPH, DVM, Amy Grice, VMD, Michael Erskine, DVM, Dipl. ABVP, Emily Graves, VMD, Dipl. ACVIM, Wendy Vaala, VMD, Dipl. ACVIM, Richard C. Tully, DVM, Dennis D. French, DVM, Ph.D, Dip. ABVP, Richard Bowman, DVM, Ray M. Kaplan, DVM, Ph.D, Dipl. ACVM, Dipl. EVPC: AAEP Parasite Control Guidelines. (PDF) AAEP, December 27, 2016, accessed on December 27, 2016 (English).
  5. ↑ Donato Traversa, Georg von Samson-Himmelstjerna, Janina Demeler, Piermarino Milillo, Sandra Schürmann: Anthelmintic resistance in cyathostomin populations from horse yards in Italy, United Kingdom and Germany . In: Parasites & Vectors . tape 2 , no. 2 , January 1, 2009, ISSN  1756-3305 , p. S2 , doi : 10.1186 / 1756-3305-2-S2-S2 , PMID 19778463 , PMC 2751838 (free full text).
  6. ↑ BM McGraw & JOD Slocombe (1976): Strongylus vulgaris in the horse: a review. Canadian Veterinary Journal vol. 17, no. 6: 150-157.
  7. ^ Ray M. Kaplan (2002): Anthelmintic resistance in nematodes of horses. Veterinary Research Volume 33, Number 5: 491 - 507 doi: 10.1051 / vetres: 2002035
  8. ↑ MK Nielsen (2009): Restrictions of anthelmintic usage: perspectives and potential consequences. Parasites & Vectors 2 (Suppl 2): ​​7-14.