Exam 3: Managing Parasites in Small Ruminants

define smart drenching

• an approach whereby we use current state of knowledge regarding host physiology, anthemintic pharmacokinetics, parasite biology, dynamics of selection for resistance, resistance status of worms on farm → to develop strategies that maximize effectiveness of treatments while decreasing selection of drug resistance 

proper dose/drenching technique

• ensure proper dose is delivered and lodges in the rumen

• if drench is delivered in the buccal cavity, can stimulate closure of the esophageal groove causing the drench to bypass the rumen

host physiology to maximize efficacy

• restrict feed intake for 24hrs prior to treatment

• once in the rumen, the duration of the drug effect is largely dependent on the flow rate of the digesta

• decreasing digesta transit leads to an increase in drug contact with worms and increased efficacy

Proper drug dosage and administration

• goats metabolize faster, should be given 1.5x levamisole and 2x any other drug

• administer all orally (pourover doesnt work and injectable causes resistance)

• combinations of 2-3 anthelmintics currently advised where resistance present, especially for cases in quarantine but selective treatment advised

introducing new small ruminants to herd without buying resistant worms 

• all new additions should be quarantined and aggresisvely dewormed upon arival with at least 2 anthelmintics with different mechanisms 

• should remain in quarantine for 10-14 days, perform FEC 

• if quarantine not possible, confine 48hrs 

impact of selective treatment on refugia 

• the more of the population that is in refugia, the slower the rate with which resistance develops 

• selective treatment significantly increases the refugia 

how do we achieve selective treatment

• fecal egg count

• FAMACHA for H. contortus, indirectly evaluate worm burden by level of anemia

FAMACHA system

• eye color chart with five color categories

• compare chart with color of mucous membranes of sheep or goat

• 1- not anemic

• 5- severely anemic

concept behind selective treatment 

• worms are not distributed equally in groups of animals, and 20-30% of animals harbor most worms

• in targeting anemic animals, indirectly targeting many of the high egg counts 

recommendations for proper FAMACHA use

• check both eyes and score on lowest

• no ½ score, assign lower if unsure

• do not hold more than a few seconds

• keep records

how to integrate the FAMACHA system

• start examining at tw week intervals in the spring, treat categories 4 and 5

• go in one week intervals as ncessary during Haemonchus season

• if >10% of flock 4 and 5, consider treating 3s as well

• do not treat all anmals before moving them

• examine animals that lag behind the herd

• check for bottle jaw and treat regardless of anemia

precautions when using FAMACHA 

• paleness or reddening may have other causes such as other parasites, nutritional deficiencies, enviornmental conditions, infectious eye diseases 

• only properly trained persons should apply 

• card is an aid in control of Haemonchus only, replace card after 12 months 

• system is best used by producers where back up assistance is available from a veterinarian 

alternative methods for worm control

• breeding for resistance

• copper oxide wire particles

• condensed tannin-containing plants

• worm trapping fungi

• vaccines

• integrated strategies

breeding for resistance

• select resistant individuals using FEC and FAMCHA and cull susceptible

• use resistant breeds such as Barbados blackbelly, Suffolk sheep

• long process but rewarding

copper oxide wire particles for parasite control 

• Haemonchous only 

• markeded for use in cattle and small ruminants where copper deficiency is common 

• potentially more toxic in sheep than goats 

• works synergistically with dewormers 

• selective treatment 

condensed tannin containing plants for parasite control

• sericea lespedexa- establishment as pasture, hay, meal, pellets, ect

• Bordsfoot trefoil

• plant extracts drench or in pelleted feed

worm trapping fungi for parasite control

• Duddingtonia flagrans

• affects all worm larvae

• feed daily with supplement

• primary objective is to clean pasture

vaccines for Haemonchus 

• barbervax works well in sheep but not goats

• drawback is that vaccination has to be done 4-5x per year 

• refined product developed but will not be marketed in US

integrated strategies for control of Haemnchus

• use FAMACHA/FEC for monitoring infection level

• cull high infection for resistance selection

• deworm using smart drenching

• reduced stocking rate, mized species grazing, dry lot, pasture spelling, browse for goats

• worm trapping fungus

what is Moniexia expansa

• cestode, long and ribbon like with segments

• life cycle is indirect and infective stage is in intermediate host (orbidatid mite)

• located in small intestines of animals <1 year old

pathology of Moniezia expansa 

relatively nonpathogenic, but heavy infections cause unthriftiness, diarrhea, intestinal obstruction 

treatment of Moniezia expansa

• albendazole (a benzimidazole)

life cycle of Moniezia expansa

• host ingested infected mites

• cysticercoids, which are freed during digestion, attach to intestinal wall and mature

• mature cestodes in small intestines

• gravid segments break off and pass in feces

• mite ingests infective eggs, which hatch and develop into cysticercoids

snail and snail habitat for Fasciola hepatica 

• mud snail family Lymnaeidae 

• Galba cubensis and Galba bulimoides 

• neutral soils 

• reasonably moist through the year

• temperature >50 

anthelmintic resistance in Fasciola hepatica

• reported in countries outside the US in Triclabendazole and Albendazole

• no reports from the united states but no studies have been done

factors to consider in the management of F. hepatica infections

• history

• extent of snail habitat

• season of year

• age group

• stocking rate

• nutrition

• presence of clinical disease

• strategies to fence off infective pasture may be difficult to implement

• avoiding grazing infective pasture difficult

treatment and control of Fasciola hepatica in US 

• Albendazole in beef cattle, sheep and non lactating goats 

• Cloirsulon with ivermectin in cattle 

• both products only effective against adult flucks 

diagnosis of Anthelminti resistance of Fasciola hepatica

• livers condemned at slaughter despite treatment

• measurement after treatment of fecal egg count reduction or copro-antigen ELISA

• egg hatch test

optimal treatment for gulf coast F. hepatica

adults in october, november, december

optimal treatment for pacific northwest F. hepatica

• adults in april and may

what affects likelihood of resistance in Fasciola hepatica 

• greater with whole flock treatments 

• increased when flukes in refugia are low → snails in aestivation or hibernation, most flukes are adults in hosts 

• use of whole flock treatments with albendazole may have inadvertent consequence of selecting for resistance n H. contortus 

treatment recommendations for Fasciola hepatica

• always consider as differential for anemia, hypoproteinemia, loss of condition

• check efficacy for treatment by performing fecal exam 7, 14, 21 days after treatment

• avoid whole flock treatments, treat ½ at a time 2 weeks apart

• treat individuals with clinical signs

pathogenic coccidia in sheep

• E. crandalis

• E. ovinoidalis

pathogenic species of coccidia in goats 

• E. ninakohlyakiovae

• E. caprina 

coccidia life cycle

• host ingests sporulated oocysts

• oocysts excyst, and sporozoites invade cecal or intestinal epithelial wall

• meronts form in epithhelial cells

• asexual meront stage may continue for several generations

• macrogametes and microgametocytes form

• microgametes break out of microgametocytes and fertilize macrogametes,and fertilized zygotes rupture from epithelial cells

• oocysts in feces

presentation of coccidiosis in small ruminants

• in sheep, associated with shipping

• may see profuse diarrhea streaked with blood

• goats appear to be much more susceptible than sheep

• lambs and kids

• dehydration may lead to deaths

treatment of coccidiosis in small ruminants 

• sulfa drugs may be used, supportive therapy 

• coccidiostats like ionophores may be used to prevent, Allow infection to occur and immunity to development but not clinical disease 

• minimize stress