THE IMPACT OF INTERNAL PARASITES ON FLOCK HEALTH AND PRODUCTIVITY

SUSAN SCHOENIAN

Sheep and Goat Specialist

University of Maryland Extension

sschoen@umd.edu – www.sheepandgoat

INTERNAL PARASITESGASTRO-INTESTINAL PARASITES, NEMATODES, WORMS

Internal parasites are the primary health problem of sheep raised in warm, moist climates or during periods of warm, wet weather.

Parasite risk varies by geographic area, year, season, and production practices.

Internal parasitism is exacerbated by the widespread development of anthelmintic-resistant worms (caused by over-reliance on and misuse of anti-parasitic drugs).

MANY INTERNAL PARASITES CAN AFFECT SHEEP.

1. Nematodes (roundworms) Haemonchus contortus (barber pole)

Trichostrongylus

Teladorsagia (Ostertagia)

Nematodirus

Meningeal worm

Lungworms

2. Trematodes (flatworms) Tapeworms - Moniezia expanza

Flukes - Fasciola hepatica

3. Protozoa Coccidia - Eimeria spp.

THE BARBER POLE WORMHAEMONCHUS CONTORTUS

Originally thought of as a tropical parasite, the range of the barber pole worm is expanding, as the parasite is adapting to more northern climates (because of climate change ?).

The blood-sucking barber pole worm is deadly. It is usually the most pathogenic parasite affecting small ruminants.

The barber pole worm probably causes more death losses (in small ruminants) than any other parasite worldwide.

ANTHELMINTIC RESISTANCEABILITY OF WORMS IN A POPULATION TO SURVIVE DRUG TREATMENTS THAT ARE GENERALLY EFFECTIVE AGAINST THE SAME SPECIES AND STAGE OF INFECTION AT THE SAME DOSE RATE.

Anthelmintic resistance has been reported in all sheep-raising countries of the world.

Worms have developed resistance to all dewormers and dewormer classes.

There is cross-resistant among drugs in the same class; worms develop resistance to mode of action, not specific drug.

Some farms are experiencing total anthelmintic failure.

Less is know about anthelmintic resistance in Canada and Alberta.

< 95% reduction in FEC = suspected resistance< 90% reduction in FEC = resistance

ANTHELMINTIC RESISTANCE IN USA

PILOT STUDY IN ALBERTA (SUMMER 2014)

Farm # Mean FEC

1 1623 27534 4585 8377 562

11 39212 98313 27115 70016 32218 819 820 252021 109122 160423 152024 450725 271

Fenbendazole Ivermectin

Farm % reduction 95% CI % reduction 95% CI

7 16 0-81 77 10-94

15 70 13-91 41 0-79

20 38 0-71 78 33-93

24 -94 0-20 -34 0-47

Source: N’ewesletter, January 2015, Alberta Lamb Producers

CONCLUSIONS OF PILOT STUDY

As evidenced by high egg counts in ewes, many Alberta sheep flocks have high parasite burdens.

Many Alberta farms have resistance to fenbendazole (benzimidazole) and ivermectin (macrocylic lactone -avermectin).

The high egg counts could be indicative of a heavy burden of Haemonchus contortus (barber pole worm) on some farms.

A larger study is planned to confirm preliminary findings and provide a detailed picture of the prevalence, distribution, and anthelmintic sensitivity of GI parasites in Alberta sheep.

TWO PRIMARY TESTS TO DETERMINE ANTHELMINTIC RESISTANCE (AR)

1. In vivoFecal egg count reduction test

Compare before and after treatment fecal egg counts of treated and untreated (control) animals for each drug.

2. In vitroLarval development assay (LDA)DrenchRite® test

Lab test that uses a pooled fecal sample to detect anthelmintic resistance to four different anthelmintic groupings.

FECAL EGG COUNT REDUCTION TEST (FECRT)

Compare before and after fecal egg counts (10-14 d): Calculate percent reduction in FEC

<90% = resistance present <95% = resistance suspected

High variability after 95%.Most accurate when results are between >97 and <60%.

Few animals and lower egg counts increase variability (and bias) of results.

Need groups of 15 animals (lambs=best, >200 epg) not dewormed for previous 8-12 weeks .

Evaluates one drug, one dose

Local vet or diagnostic lab can do; producer can learn to do.

DRENCHRITE® ASSAYLARVAL DEVELOPMENT ASSAY (LDA)

Labor-intensive lab testa. Utilizes eggs isolated from feces from infected animals.

b. Eggs are placed in well assay plate.

c. The plates have doubling concentrations of different drugs in them, along with “no drug” controls.

d. Eggs are hatched to 3rd stage larvae.

e. At end of incubation period, the plate is examined .

Samples (from about 10 animals, >200 epg) need to be properly collected and shipped.

Determines resistance or suspected resistance for four drench groups.

Identifies parasite species from larvae, e.g. % Haemonchus

Test is done by Dr. Ray Kaplan’s lab at the University of Georgia Vet School.

COMPARISON OF TESTS

FECRT

Tests one drug, one dosage

Egg count is for all strongyle-type worms

Need more animals to sample

More practical, but requires considerable on-farm work Veterinarian or diagnostic lab can

do fecal egg counting. Producer can learn to do

Cost varies; more expensive than LDA if you pay to have fecal egg counts done (US$3-20 per sample).

DRENCHRITE® - LDA

Tests all drug groups simultaneously- Resistance to moxidectin is estimated

Identifies worm species by %

Requires fewer animals, ~10

Expensive (?) - $450

University of Georgia is only lab in US that does DrenchRite test.

Alberta (x), elsewhere in Canada (?)

THE PRIMARY COST(S) OF INTERNAL PARASITISM MAY BE SUB-CLINICAL

Reduced milk production

Reduced growth rates

Reduced feed and grazing efficiency

Gut motility (tapeworms)

Increased days to market

Reduced wool growth

Lower body condition

Increased dag scores/higher breech scores

Reduced feed intake

Reduced immunity to other disease conditions.

MODELING EFFECTS OF INTERNAL PARASITISM

For a project in Mexico, Dr. Dave Notter (VA Tech, retired) modeled the effects of internal parasitism on grazing lambs.

In Mexico, there are large regional differences in parasite challenge, drug resistance is prevalent, making intensive use of chemical dewormers ineffective, and there are both highly susceptible and resistant breeds in the sheep population.

He presented this series of graphs at the 2014 Southwest Virginia Sheep Field Day & Ram Sale.

MODELING THE EFFECTS OF INTERNAL PARASITISM

MODELING THE EFFECTS OF INTERNAL PARASITISM

MODELING THE EFFECTS OF INTERNAL PARASITISM

MODELING THE COSTS OF INTERNAL PARASITISM

MODELING THE COSTS OF INTERNAL PARASITISM

MODELING THE COSTS OF INTERNAL PARASITISM

MODELING THE COSTS OF INTERNAL PARASITISM

MODELING THE COSTS OF INTERNAL PARASITISM

PRODUCTION COST OF ANTHELMINTIC RESISTANCE (New Zealand, 2012)

Ten farmlets, each stocked with 30 lambs, were used to determine economic impact of anthelmintic resistance.

Lambs were grazed for five months and dewormed monthly with either albendazole, to which resistance existed, or a new combination product (derquantel + abamectin) to which there was no resistance.

Productivity measures were determined on five farms.

Anthelmintic efficiency was measured at last two dates.

DrugTrichostrongylus

spp.Teladorsagiacircumcincta

Albendazole 48.4% 40.9%

Combination >99% >99%

PRODUCTION COST OF ANTHELMINTIC RESISTANCE (New Zealand, 2012)

(---) Highly-effective drench (combination: derquantel + abamectin)(__) Ineffective drench (albendazole)

Parasite species: trichostrongylus, teladorsagia, and nematodirus

PRODUCTION COST OF ANTHELMINTIC RESISTANCE (New Zealand, 2012)

Improved performance of lambs treated with effective dewormer

+ 9 kg (4.1 lb.) live weight gain

+ 4.7 kg (2.1 lb.) carcass weight

+ 10.4% increase in carcass value

Time required for 50% of lambs to reach target weight (38 kg/83.6 lbs.) was significantly shorter (17 days) in animals treated with effective dewormer.

Significant differences in body condition scores, breech scores, and fleece weights were also recorded -- all in-favor of lambs treated with effective dewormer.

COST-BENEFIT OF ANTHELMINTIC PROTOCOLS

Group Anthelmintic protocol

Group A (n=10)

Without drug rotationLevamisole every 60 d

Group B (n=10)

With drug rotation Levamisole at months 2, 4, 8, and 12; albendazole at month 6

Group C (n=10)

Targeted Selective Treatment (TST)Treated according to FAMACHA© (4,5)or FAMACHA© + body condition score (3)

One year study at a farm in Southern BrazilPrimary species: Haemonchus contortus, Trichostrongylus , Teladorsagia (Ostertagia)

Source: Acta Scientiae Veterinariae, 2014

COST-BENEFIT OF ANTHELMINTIC PROTOCOLS

Group ABi-monthly, no rotation

Group BBi-monthly, rotation

Group CFAMACHA© (selective)

Unnecessary cost of 66.6%Increased selection for resistant worms (LEV)

7.4% lower cost than AUnnecessary cost of 63.3%Increase selection for resistant worms (LEV, ALB)

Lower fecal egg counts49.6% lower cost than A

Reduce use of anthelmintics

Less treatment costsReduced selection for resistant parasitesReduced chance of drug residues Best cost-benefit ratio

**Constant management**

Source: Acta Scientiae Veterinariae, 2014

EFFECTS OF INTERNAL PARASITISM ON NUTRITION

Nutritional requirements (NRC) are generally for confined animals, e.g. low parasite burden.

Internal parasitism affects both energy and protein (and amino acid) requirements of sheep.

There is need for more information on the consequence of internal parasitism on nutritional requirements.

EFFECTS OF INTERNAL PARASITISM ON NUTRITION (ENERGY)

Effects of parasitism on MEm have not been well

quantified, but is thought to involve a decrease in Km as a

result of increased turnover of GI tract protein, apart from

frequent occurrences of reduced feed intake.

Immune response to parasites could have nutritional costs

as high as 15% of maintenance needs, which is supported

by decreased wool growth by sheep selected for resistance

to internal parasitism.

An example cost of 5% has been calculated.

Nutrient partitioning during pregnancy and lactation

compromises ewe’s ability to resist parasite infection.

K = efficiency

EFFECTS OF INTERNAL PARASITISM ON NUTRITION (PROTEIN)

Decreased feed intake in response to internal parasite would entail an increase metabolizable protein requirement both on an absolute and dietary concentration basis.

Numerous studies now support the view that providing supplemental metabolizable protein to sheep with subclinical infections of GI parasites improves their resistance and resilience to parasites.

The response to supplementation is greater when the protein source is not extensively degraded, i.e. by-pass protein, e.g. fish meal.

Requirement for sulfur-amino acids will be greater (benefit of methionine supplementation demonstrated).

WHAT WE DON’T WANT TO HEAR

Anthelmintic resistance is real.

Anthelmintic resistance is widespread.

Anthelmintic resistance is increasing

Anthelmintic resistance is permanent.

There is multiple drug resistance.

Anthelmintic resistance is inevitable; all we can do is affect the rate at which it occurs.

Sequential deworming and combination dewormers are only a short-term “fix.”

Anthelmintics (dewormers), including new ones (Zolvix®/monepantel) are not the answer to controlling parasites.

THANK YOU FOR YOUR ATTENTION.QUESTIONS? COMMENTS?

SUSAN SCHOENIANSheep & Goat SpecialistUniversity of Maryland Extensionsschoen@umd.eduwww.sheepandgoat.comwww.wormx.info