Impact of Parasitic Disease for the Veterinarian Thomas M. Craig

Texas A&M University

14 July 2016 at Beni-Suef University

What does the Vet need to know? • What are the important hosts in your area

• Which parasites are in the practice area

• Which age of host is at risk

• When are the parasites transmitted

• What the parasite does to the host

• How the parasite survives out of or in the host

• What treatment, if any, is effective

• Who benefits from treatment

What a Vet needs to Know

• Example: cattle in semi-tropical gulf coast of Texas

• Most cattle are raised for production of beef not milk

• Cattle on pasture day and night 365 days a year

Are Worms important?

• Worms live in the gastrointestinal tract or elsewhere in cattle

• They may interfere with normal body functions so that the animal does not have a good appetite, convert feed to nutrition, remove blood and serum, encourage proliferation of bad bacteria

• A few cattle may suffer clinical disease (even death), others do not grow, produce milk, or reproduce to their genetic potential

Cattle worms in 2016 Texas Gulf Coast

• Lungworms: almost disappeared in the year 32 AI

• Tapeworms: disgusting, vaccinate calves for Clostridia toxins, don’t let people defecate where cattle eat

• Liver flukes: only if you have them, then treat to protect the snails

• Gastrointestinal nematodes: can be important if it rains

Gastrointestinal Nematodes

• Live in the abomasum, small or large intestine • Each species makes its living in a different way and

does different things to the host • They all produce eggs which hatch in the fecal pat,

and the larvae feed on bacteria, the larvae require a minimum of one to two weeks to feed, molt and become infective

• Infective larvae leave the fecal pat in water and ascend vegetation where they are grazed

Worm Characteristics

Ostertagia

u Greatest economic importance

u Throughout US except far south FL, TX

u Arrested larvae survival mechanism

u Calves and adults affected

Cooperia u Young calf pathogen if ≥ 20,000 worms

u Mature cattle resist infections

u Tolerant of macrocyclic lactones Prolific egg-layer

Haemonchus

u Most prolific egg layer

u Voracious blood feeder

u Calf pathogen

u Coastal bermudagrass developed for Haemonchus

Ostertagia ostertagi (brown stomach worm)

• Temperate climate transmission

• Transmitted in pastures late October until May in gulf coast states

• Transmitted in pasture from April until November in remainder of country

• Survives summer in the south, or the winter in the north as arrested larvae in abomasal glands

• Larvae do no damage while arrested

Why Is Ostertagia Important?

• May cause disease in cows as well as calves

• Arrested Ostertagia survive in the abomasal glands as inactive larvae

• Larvae are programmed to arrest by environmental clues

• Larvae emerge from arrest in the autumn or spring when conditions on pasture are favorable for transmission

• Emergence of larvae causes damage to the abomasum

• Larvae rapidly become adults which produce eggs that contaminate the pasture

Ostertagia ostertagi

adult

L4

in out

Infected gland

Normal glands Infected glands

Small larvae (L4) deep in glands, Larger (adult worm) emerge from glands

Ostertagia

• Abomasal edema • Proliferation of bacteria in the abomasum • Fermentation in the small

intestine • Fluid pulled into gut, diarrhea • Dehydration • Primary digestion decreased • Anorexia • Depressed immunity

Which pasture has the most grass? Which animals had more worms?

Treated Parasitized

treated untreated

Haemonchus Barbers pole Worm

• An important parasitic helminth of calves in humid tropical climates i.e. hot humid summers

• Older cattle become resistant to and/or tolerant of infection

• Voracious blood sucker: causes anemia and hypoproteinemia, may exsanguinate calves

• Extremely fecund 5,000 to 6,000 eggs/female/day

• Problem on high intensity summer grazing systems

Adult Haemonchus in Abomasum

Who are Cooperia? small intestinal parasites

• Eggs passed in the feces of cattle less than a year of age are predominantly Cooperia

• Stimulate early resistance by calf to infection

• Causes disease in calves (diarrhea) if 20,000 or more worms in the small intestine

• Are tolerant of macrocyclic lactones

• Importance? Dairy calves, light weight stocker calves; probably so! Others; probably not!

Cooperia spp.

Cooperia spp.

Small intestine calves

Worm Infections where did they come from?

• Where are you geographically?

• What is the time of year?

• What was the rainfall or irrigation in the last two months?

• Is the stocking density 1 cow calf unit per acre or per section?

• How much nutrition is there in the forage and or supplements?

• Where did you import your worms from?

Geography, Climate, Parasites

high rainfall >32 inches annual rainfall, parasite paradise low to medium >16 inches, few parasites very low rainfall depends on range, few if any

Stocking Rate

Stocking Density

Who is on the Pasture?

• Cows and calves?

• Replacements?

• Stockers?

• Other species? To determine who is sharing what with whom

• Who brought something with them?

• Who is eating most of the forage?

• Who is at risk?

Risk

• The answers to the questions will give you an idea of the relative risk of having sufficient numbers of worms to cause economic or clinical disease

• Clinical disease due to gastrointestinal parasites in adult cows is rare. Usually due to concurrent malnutrition or lack of prior experience with the worm

• Economic parasitism manifest as lowered milk production and lower calf weights likely on many properties

Numbers Count

• Parasitic disease is a numbers game

• A. Few = stimulate protective immune response

• B. More = tolerated by most, economic loss in others

• C. Large numbers = clinical or economic loss

• Different numbers for each parasite species

• Different numbers for each class of cattle

Factors That Contribute to Economic Parasitism in Cattle

• Age of cattle

• Level of exposure by naïve cattle

• Breed and local environment

• Season of calving

• Age at weaning

• Source of cattle and parasites

• Quality and quantity of diet

Stocker Calves

• Stocker calves are weaned growing cattle destined to being eaten by humans. Raised on pastures or feedlots

• When stocker calves are gathered not only do they have the parasites they bring with them but acquire parasites of calves from other farms they are mixed with as well as the parasites remaining on the pastures

• All contribute to problems

• Highest risk for disease and anthelmintic resistance occurs on permanent pastures in stocker / background calves

Stocker or Replacement Calves

• Cooperia most numerous; macrocyclic lactones may not be effective against this genus but immunity will eventually control

• Haemonchus problem in high density summer grazing evidence of macrocyclic lactone and or benzimidazole resistance

Stocker or Replacement Calves

• Group most likely to suffer from disease and will benefit from treatment

• Treatment with anthelmintic before being released onto seasonal pastures

• Treatment before and after being released onto permanent pastures

• The timing of retreatment depends on the residual effects of the anthelmintic used and season

First Calf Heifers

• Still growing

• Feeding a suckling calf

• Trying to become attractive to the bulls

• Have not yet become resistant to some worm species

• Competing with older cattle?

• Most likely to suffer from clinical and or economic parasitism

Adult Beef Cows

• Rarely have clinical signs associated with internal parasitic infections

• If there are sufficient numbers of specific parasites i.e. Ostertagia ostertagi cows rest more and eat less

• Resting cows produce less milk

• Calves weigh less at weaning

Bulls

• Generally more susceptible to gastrointestinal nematodes than cows

• Remember hormones are raging year around

• May not be treated when other cattle are

Perceived Parasite Problem?

• Ill thriven cattle - ADR "ain't doen right"

• “Elevated” worm egg counts

• Lack of a “response” to anthelmintics

• Compare to similar animals under similar conditions

Why use Anthelmintics? Who do we treat?

• Why 1) To save lives 2) To increase profits 3) To protect pastures

• Who 1) Those cattle which contribute most to pasture contamination 2) Those suffering from disease

Who Should be Dewormed?

• Cows or calves? • Cows; As geography and management dictate • Calves; When you treat cows if more than100 kg. and at

weaning • Use different drugs depending on age and parasites you

are trying to control • First calf heifers and bulls if nothing else in herd

• Fluke infected cattle in south autumn, north spring:

common fluke; Ivomec Plus (Ivermectin + Clorsulon), Deer fluke; Valbazen (Albendazole)

How Often Should Cattle be administered anthelmintics? • Where do you live?

• South: spring, early summer • North: late fall, winter • Tropics: before the onset of the rainy season • Lower the number of reproducing nematodes

contaminating the pastures • What is the stocking rate? • The higher the rate the greater the exposure, if all

things are equal

Should The Drug Differ for Cows and Calves?

• When calves are suckling the same worms are on the pasture but who is acquiring them?

• Do not use macrocyclic lactones in suckling calves, great anthelmintics for mommy!

• Before and at weaning; calves have Cooperia rare in cows

• Benzimidazoles are the best choice for Cooperia, not most other worms

• Do you have adult flukes? Treat adult cattle

Evaluation of Worm Numbers Fecal Egg Counts

• Somewhat linear correlation between level of infection by adult worms and egg count

• Species vary in fecundity • A few Haemonchus produce more eggs than an

abomasum full of Ostertagia

• Some worms damage host as larvae others as adults

• Larvae don't produce eggs

Worm Eggs that Look the Same

Cooperia Haemonchus Oesophagostomum Ostertagia Trichostrongylus

When Should Fecal Egg Counts be Performed?

• Prior to entering a rested pasture to know what they are carrying into the pasture

• Six to Eight weeks following the onset of grazing in pasture by at risk animals so the parasites picked up early will be reproducing adult worms

• When cattle appear to have possible nematode associated disease

• At the time of anthelmintic treatment and again in two to four weeks to estimate drug efficacy

How Do We Differentiate Among Worm Eggs?

• Geography, time of year and class of cattle will give you an idea of which parasite species are there

• Larvae hatch from eggs develop to the infective stage, infective larvae may be morphologically differentiated (Coproculture) takes 2 weeks in cattle

• Genetic testing sensitive but limited laboratory availability at this time

Do Anthelmintics Always Work In Cattle?

• Cooperia punctata, primary culprit for tolerance / resistance in calves • Economic importance? • Calf just needs to get older

• Haemonchus populations resistant to both macrocyclic lactones and benzimidazoles on intensely grazed permanent pastures by calves

• Report in California Ostertagia resistance, scary thought

How Do We Know if an Anthelmintic Works on a Property?

• Treat some animals don't treat others slaughter and look for worms in the GI tract two weeks later

• The species of parasite and stage of development can be compared

• Great test but not practical

• Determine if there are worm eggs present prior to treatment and then compare the number of eggs present 2 to 4 weeks later; (FERT) Fecal Egg Reduction Test next best

Fecal Egg Reduction Test (FERT)

• An indicator of efficacy • Best done in younger cattle • Mean difference of fecal egg counts in a population

at treatment and 2 to 4 weeks later • Uneven distribution of egg counts • 20% of herd has 80% of eggs

• 20 individual fecal samples at random or 10 individually identified samples

• Identify the genera of worms both before and after treatment

Fecal Egg Reduction Test Calves 2015

Group 5/20 7/7 9/14

Control 286 73

FERT % Reduction 75.4

EPR 213 55 32

FERT % Reduction 74 85

DEC 210.5 47.8 65

FERT % Reduction 77 69

Example Dairy Calves

• Calves on pasture north east TX

• October: 1. control 2. macrocyclic lactone 3. combine; macrocyclic lactone and benzimidazole

• Fecal samples: 1) treatment, 2) two weeks, 3) one month

Dairy Calves – Fecal Egg Reduction Test

FECRT (eggs/gm) Treatment Group Treatment 2 weeks 1 month

Control *697 *875 *1650

FERT % Reduction -26 -137

Macrocyclic Lactone 815 473 1032

FERT % Reduction 42 -27

Combine BMZ + Macro Lac 924 146 266

FERT % Reduction 84 71

Dairy Calves Texas Haemonchus

placei H. placei Cooperia

punctata Cooperia punctata

Ostertagia Nematodirus Trichuris

Adult L4 Adult L4

Control 2483 33 15008 250 17 33 17

Injectable Macrocyclic Lactone

667 0 6000 8 0 0 0

% 73 100 60 97 100 100 100

Combination 419 0 19 13 0 0 0

% 83 100 99.9 95 100 100 100

Stocker Calves

• Stocker operation central Texas

• Calves on pasture

• Treated April :

• 1) control 2) macrocyclic lactone

• No fecal egg counts at time of treatment

Stocker Calves Central Texas Haemonchus

placei Ostertagia ostertagi

Trichuris axei Cooperia punctata

Cooperia punctata

Adult Adult Adult Adult L4

Control 133 1146 8.5 3475* 94

Injectable Macrocyclic Lactone

479 0 0 2384 0

% Reduction -260 100 100 32 100

*intestine thickened one calf from an allergic reaction possibly self cure, no worms recovered

Does It Matter Injectable, Pour-on, or Oral?

• Injectable: long residual effects, injection site reaction

• Pour-on: quick easy, must be absorbed or licked

• Oral: drench or feed, adequate dose for each animal

• The most effective is the method that gets the proper dose to the target worm with the least stress on the cattle and the owner

Resistant Worms in Cattle? So What?

• No evidence of important resistance in cow calf operations; yet!

• Calves have tolerant / resistant Cooperia but the cows act as biological controls

• If resistant Haemonchus imported the cows generally tolerate infections and clean worms from pasture but parasites remain a threat