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Parasitology

Scenario

A wealthy retired businessman has decided to start an organic farm in Snowdonia, North Wales. He does not intend to get his own hands dirty and you are deputed to look after the health of his hundred strong flock of sheep. He stipulates that no antibiotics or man-made chemicals should be used at any time. What are the parasites you need to consider and what would you do to control and treat them?

Stocking Rate

Faecal egg counts

  • = number of livestock per unit area

  • There is a direct relationship observed between increased stocking rate and increased parasitism.

  • To prevent this there must be improved pasture production and pasture growth

Introduction

Economical Aspects

•Uses faeces samples to determine level of parasite infection

•Can also identify species of parasite

•High egg count = high parasite burden

•Low egg count = low parasite burden

•Can indicate infection present before clinical signs appear

  • Attributes

  • Parasitic Infections

  • Anthelmintic resistance

  • Costs compared to non organic
  • Black Welsh Mountain Sheep (Ovis aries)
  • Snowdonia
  • Fenced area
  • Holistic treatment

Macmaster slide used for faecal egg counts

Faeces samples and eggs present

Conclusion

Within the organic farming objective; grazing management and biological control are important components for future parasite control schemes in grazing livestock

Although man-made drugs are more reliable for control, resistance to worming groups is becoming an issue.

Holistic methods are currently not prone to the same resistance

Fencing

  • Isolating high risk or infectious areas (lakes, boggy areas)

  • Long term financial savings.

Grazing Management

  • Browsing resources – pasture management

  • Parasites are found in the first 2 inches of vegetation

  • High –protein feed – improves host resistance

Endoparasites to consider

with the highest prevalence

and pathogenicity in sheep

Livestock Rotation

References

=Rotating stock between pastures

  • Preventative –putting worm-free stock onto clean pasture * normally combined with drugs
  • Evasive –movement of stock just before the larvae from contamination are likely to appear in high numbers
  • Diluting – placing susceptible animals with a high number of naturally resistant animals
  • species interchange systems

Methods of control and Treatment

Abbott, D. K. A., Taylor, P. M. & Stubbings, L. A., 2009. Sustainable Worm Control Strategies for Sheep. 3rd ed. s.l.:SCOPS (Sustainable Control Of Parasites in Sheep).

Athanasiadou S, G. D. (2011). The use of chicory for parasite control in organic ewes and their lambs. pub med US National Library of Medicine National Institutes of Health , 299-307.

Black Welsh Mountain Sheep’s Association. 2010. The Breed. [online] Available at: http://www.blackwelshmountain.org.uk/breed. [Accessed on 5th March 2013]

Gunn, A. & Pitt, S. J., 2012. Parasitology. An Integrated Approach. s.l.:Wiley-Blackwell.

Kaufmann, J., 1996. Parasitic Infections of Domestic Anim (Sathor, 2012)als: A Diagnost (Sathor, 2012)ic Manual. s.l. (Sathor, 2012):ILRI (aka ILCA (Sathor, 2012) and ILRAD).

Knox, M. (2008). Effectiveness of copper oxide wire particles for Haemonchus contortus control in sheep. Australian Veterinary Journal , 224-227.

Mapes, C. J. & Coop, R. L., 1970. The interaction of infections of Haemonchus contortus and Nematodirus battus in lambs: I. The effect of massive infections of Haemonchus on subsequent infections of Nematodirus. Journal of Comparative Pathology, 80(1), p. 123–136.

Morris, M. C., 2000. Ethical Issues Associated With Sheep Fly Strike Research, Prevention, and Control. Journal of Agricultural and Environmental Ethics, 13(3-4), pp. 205-217.

Roberts, E. W., 1950. Studies on the life-cycle of Fasdoia hepatica (Linnaeus) and of its snail host, Limnaea (Galba) trnncatala (Müller), in the field and under controlled conditions in the laboratory.. Annals of Tropical Medicine and Parasitology , 44(2), pp. 187-206.

Sanders, A. B., How, S. J., Lloyd, D. H. & Hill, R., 1990. The effect of energy malnutrition in ruminants on experimental infection with dermatophilus congolensis. Journal of Comparative Pathology, 103(4), p. 361–368.

Sathor, T. (2012). Pros and Cons: A Debators Handbook . In T. Sather, Alternative Medicine (p. 280). Routledge.

Stear, M. J., Park, M. & Bishop, S. C., 1996. The Key Components of Resistance to Ostertagia circurmcincta in Lambs. Parasitology Today, 12(11), pp. 438 - 441.

Snowdonia Mountain Lamb. 2013. Order Forms. [online] Available at: http://www.snowdonia lamb.f9.co.uk/TopstripFrameset2.htm. [Accessed on 5th March 2013]

Stewart, D. F., 1950. Studies on resistance of sheep to infestation with Haemonchus contortus and Trichostrongylus spp., and on the immunological reactions of sheep exposed to infestation. V. The nature of the 'self-cure' phenomenon.. Australian Journal of Agricultural Research, 4(1), pp. 100 - 117.

Taylor, S. M. & Pearson, G. R., 1979. Trichostrongylus vitrinus in sheep: II. The location of nematodes and associated pathological changes in the small intestine during clinical infection. Journal of Comparative Pathology, 89(3), p. 405–412.

Barger.I. 1997. Control by management. Veterinary Parasitology. 72,493-506

Larsen.M.1999. Biological control of helminths. International Journal for Parasitology. 29,139-146

Thamsborg.S,Roepstorff.A,Larsen.M. 1999. Integrated and biological control of parasites in organic and conventional production systems. Veterinary parasitology. 84,169-186

Torres-Acosta.J,Hoste.H. 2008. Alternative or improved methods to limit gastro-intestinal parasitism in grazing sheep and goats. Small Ruminant Research. 77,159-173

Waller.P.1993. Towards sustainable nematode parasite control of livestock. Veterinary Parasitology. 48,295-309

Waller.P,Thamsborg.S. 2004. Nematode control in ‘green’ ruminant production systems. Trends in Parasitology. 20:10

Waller.P. 2006. Sustainable nematode parasite control strategies for ruminant livestock by grazing management and biological control. Animal Feed Science and Technology. 126,277-289

Image References

Teladorsagia circumcincta (Previously Ostertagia)

– Brown Stomach worm

Slide 1 Intro - http://www.cashmeregoats.ca/user_files/images/Picture%20415.jpg & http://www.blackwelshmountain.co.uk/manor-ram.gif & http://www.johnstokesphotography.co.uk/Snowdonia.jpg

Slide 2 - Worm image - http://iranhelminthparasites.com/OVINE/o-circum1.jpg) & Egg image: http://www.viarural.com.ar/viarural.com.ar/ganaderia/ovinos/parasitos-internos/ostertagia-02.jpg)

Slide 3 - Worm image: http://2.bp.blogspot.com/-Wmv7vMkHmd4/T2A_bgTij-I/AAAAAAAAAAU/XWwXy_7iKqE/s1600/barberpoleworm.jpg & Egg image: http://www.apacapacas.com/parasites/para-site_files/53.jpgSlide 4 - Worm egg: http://www.rvc.ac.uk/review/parasitology/images/largeJPGs/Nematodirus-egg-_-p56.jpg & Worm: http://www.lightlivestockequipment.com/images/nematodirus-helvetianusegg.gif

Slide 5 - Worm & Egg: http://www.medical-enc.ru/18/images/trichostrongylus-colubriformis.jpg

Slide 6 - Fluke: http://4.bp.blogspot.com/_aoBb16P2vNQ/TIycQkU7fMI/AAAAAAAAACI/YtDWmVxQcxw/s320/fluke_med.jpg & Post mortem: http://curezone.com/upload/Liver_Flush/Forum_03/Fasciola_Hepatica.jpg & Egg: http://www.wadsworth.org/parasitology/Images/F.hep.jpg

Slide 7 - Mite: http://www.county-vets.co.uk/media/resources/psoroptes%20ovis.gif & Scab: http://www.fwi.co.uk/assets/getAsset.aspx?ItemID=5227831)

Slide 12 - Myasis Image - http://projects.exeter.ac.uk/meeg/blowflies

Slide 12 - Myasis Image - http://www.vetnext.com/search.php?s=aandoening&id=73253941305%20117

Biological controls: http://www.nablacognition.org/media/foto/5/img_5409.jpg

Faecal Egg counts: http://www.fao.org/wairdocs/ILRI/x5492E/x5492e18.jpg & http://jdflipflops.co.uk/resources/_wsb_414x242_macmasters+slide+2.JPG

Pros and Cons of Holistic Treatment

Genetic Selection

•Found within the abomasum and usually between 8-15mm in length

•T. circumcincta cause a decrease in gastrointestinal efficiency

•Causes – Anorexia, Diarrhoea, weight loss and death

•Severest effects are on lambs during their first summer

Myiasis (Fly Strike)

  • Genetic screening (DNA analysis) finding the genetic marker

  • Can produce strains of animals which are more resistant to the parasites

Teladorsagia circumcincta ova

(Sathor, 2012)

•Not species specific and results in adult flies laying eggs on the surface of warm wet skin.

•Larvae feed on tissue

•Infection attracts other flies to lay their eggs

•Very painful and uncomfortable

•Death can transpire very quickly due to infection

Teladorsagia circumcincta

mouth

parts

Effects of myiasis

Biological Control

Trichostrongylus spp.

(T. colubriformis & T. vitrinus)

– Black scour worm

  • Earthworms

  • Fungi such as Nematophagus fungus and Duddingtonia flagrans both have anti – nematode properties

  • Copper Oxide

  • Chicory

  • Organic farming with no harm to the environment.

Haemonchus contortus

– Barber’s Pole worm

Chicory - Cichorium intybus

  • Can grow up to 7mm in length

•Both species reside within the small intestine and cause damage to the intestinal wall.

•Clinical Signs of infection: Diarrhoea, inappetence and rapid weight loss.

•Severe infections can lead to death

Psoroptes ovis - Sheep Scab

•The worms can be between 20-30mm in length

•Inhabit the abomasum during larval and adult stages, ingesting blood from the mucosa

•Symptoms – anaemia, tachycardia, dyspnoea, lethargy and poor milk production

•Severe infection can lead to death due to desanguination

•A mite that causes a form of allergy dermatitis, known as scab

•Mite lives on skin feeding on bacteria and secretions

•Initial signs include noticeable discomfort and scratching behaviour

•Can develop into severe form causing loss of wool and lesions

•Although not fatal, condition is uncomfortable and can increase incidence of myiasis

Trichostrongylus colubriformis adult

and ova

Hemonchus contortus ova

Hemonchus contortus

Adult

Effects of Psoroptes ovis

Psoroptes ovis adult

Fasciola hepatica (Liver Fluke)

•Requires intermediate host - Galba truncatula (Mud snail)

•G. truncatula requires muddy, acidic condition to survive. E.g. areas of poor drainage

•Conditions also allow liver fluke to flourish

•Damages the liver and bile ducts of sheep which it survives in.

•3 levels of infection: Acute, Sub-Acute and Chronic

•Symptoms vary with level of infection – Anaemia, dyspnoea, weight loss, diarrhoea, ascites and death

Fasicola hepatica life cycle

Nematodirus battus

Ectoparasites to consider

with the highest prevalence

or pathogenicity in sheep

Fasciola hepatica ova

Fasciola hepatica present within a sheep's liver following post mortem

•Pathogenic infection only in lambs

•Can reach 20mm in length and found in the duodenum

•Cause atrophy of the villi

•Symptoms: diarrhoea and dehydration

•Infection will lead to death or immunity as an adult

Nematodirus battus

adult male and

female

Nematodirus battus ova

Image obtained from CDC.gov

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