Gastrointestinal nematodes in ruminantsGastrointestinal nematodes in ruminants

Epidemiological principles Integrated Parasite Management

Silvina FernándezOrganic Agriculture Centre of Canada, Nova Scotia Agricultural College, c/o Ontario Veterinary College

Epidemiological principlesEpidemiological principles

Pasture contaminationPasture contamination: : eggs passed by the animals with eggs passed by the animals with the the fecesfeces onto pasture. onto pasture. Animals responsible for the Animals responsible for the contamination of pasturescontamination of pastures

Pasture infectivityPasture infectivity: : infective larvae (L3) on pastureinfective larvae (L3) on pastureEnvironmental factors responsible Environmental factors responsible for the development, for the development, transmission, and survival of L3 transmission, and survival of L3 on pastureon pasture

L5L4L3

Adults

Life cycle of gastrointestinal nematodes

L1L2

L3

0 1 2 3 4 5 6 weeks

summer1-2

autumn 4-6

Development time from egg to L3 (inside feces)

spring 2-4

L1L2

L3

Pasture contamination and infectivity in 32 sheep flocks in Canada (May ’06 – Apr ’07)

M-J J-J J-A A S O J F-M A0

200

400

600

800

1000

1200

FEC (ewes) FEC (lambs) infectivity

0

200

400

600

800

1000

1200

epg

L3/kg DM

Larval overwintering on pasture in Canadian flocks

5 8 33* 2 3 4 8 15 160

100

200

300

400

500

600

20072006

Teladorsagia

TrichostrongylusOesophag./Chabertia

Haemonchus

Farms ID

L3/k

g D

M

Pasture contamination and infectivity in a a cow/calf farm in QC (May 1988 – Oct 1989)

May 16

Dec 15

May 24

Oct 18

0

10

20

30

40

50

60

FEC (cows)FEC (calves - yearlings)

1988 1989

hous

ing

turn-o

ut

turn-o

ut

hous

ingep

g

(adapted from Pritchard et al, 1990)

Now what..?

The crucial issue

“but, Doc, just give me a drug because what you suggest is too hard” syndrome

Ensure farmers (and vet advisors!) acceptance of IPM measures in contrast to dewormer treatments alone

Integrated Parasite Management

Bioactive forages

Biologicalcontrol

Immunity

Genetics

Nutrition

Anthelmintics(dewormers)

Integrated Parasite

Management

Monitoring

Grazing strategies

What we donWhat we don’’t know, we cannot managet know, we cannot manage……

Monitoring (FEC) at times when the flock is at highest risk (e.gMonitoring (FEC) at times when the flock is at highest risk (e.g. . ewes: lambing season; lambs and calves: midewes: lambing season; lambs and calves: mid--summer).summer).

-- will eventually allow for targeted selective treatments with inwill eventually allow for targeted selective treatments with indicators dicators currently under study, i.e. FAMACHA, BCS, periodic weighing, milcurrently under study, i.e. FAMACHA, BCS, periodic weighing, milk k yields.yields.

Monitoring for AR every 3 years (or less!) Monitoring for AR every 3 years (or less!) -- if AR already suspected: FECRT (involving advisors & if AR already suspected: FECRT (involving advisors &

researchers)researchers)

Monitoring

Refugia: proportion of the parasite population that is not exposed to a given control measure (ATH), thus escaping selection for resistance

Anthelmintics

Dose & moveDose & move concept: not advocated anymore (when whole concept: not advocated anymore (when whole flock/herd is treated), does not consider flock/herd is treated), does not consider ““refugiarefugia”” and can and can lead to AR. lead to AR.

Anthelmintics

Targeted selective treatments (TST): donTargeted selective treatments (TST): don’’t treat the whole flock!t treat the whole flock!-- ewes in good condition (BCS) and on a good nutritional level do ewes in good condition (BCS) and on a good nutritional level do not need not need

treatmenttreatment-- Target young ewes and/or those in poorer body conditionTarget young ewes and/or those in poorer body condition-- Dependable indicators for TST are being studied (e.g. milk yieldDependable indicators for TST are being studied (e.g. milk yield in goats)in goats)

RefugiaRefugia: untreated animals will void eggs from unselected worms, : untreated animals will void eggs from unselected worms, compared to the few eggs from effectively compared to the few eggs from effectively dewormeddewormed animals.animals.

OverdispersionOverdispersion: : low numbers of low numbers of individuals carry high parasite individuals carry high parasite burdens while the majority of the burdens while the majority of the population carries low burdens population carries low burdens

Number of animals

Num

ber o

f par

asite

s

1 10 20 30 40 50

Anthelmintics

99.935.299.913.8F22

99.948.099.951.5F11

Moxidectin (Cydectin®)

Albendazole (Valbazen®)

Levamisole(UoG prep.)

Ivermectin (Ivomec®)

1Coles et al., 1992; 2Dash et al., 1988

2007: First confirmed (reported) case of AR in Canada

Grazing strategies

Safe (clean) pastureSafe (clean) pasture: a pasture where the risk of accumulation of : a pasture where the risk of accumulation of parasite larvae to pathogenic levels is minimal because the parasite larvae to pathogenic levels is minimal because the pasture pasture infectivityinfectivity is nil or very low when animals are introduced on the is nil or very low when animals are introduced on the pasture.pasture.

e.g. safe pastures at turne.g. safe pastures at turn--out in spring:out in spring:Pastures not grazed by sheep the year before (in sheep farms)Pastures not grazed by sheep the year before (in sheep farms)Newly sown pasture and never grazedNewly sown pasture and never grazed

e.g. safe pastures at mide.g. safe pastures at mid--summer:summer:Pastures after the first cut for hay and not grazed by sheep thePastures after the first cut for hay and not grazed by sheep the same same year.year.Pastures grazed by other species (e.g. cattle) the same year.Pastures grazed by other species (e.g. cattle) the same year.

Grazing strategies

Preventive grazing:Preventive grazing: parasiteparasite--free animals onto parasitefree animals onto parasite--free pastures free pastures Prevents Prevents pasture contamination.pasture contamination.-- Easier in cattle Easier in cattle -- More difficult in sheep: effective More difficult in sheep: effective dewormingdeworming of adult ewes required before of adult ewes required before

turnturn--out (which can select for AR)out (which can select for AR)-- Alternation of different animals species (cattle/sheep; cattle/Alternation of different animals species (cattle/sheep; cattle/pigs; pigs;

sheep/horses)sheep/horses)

Evasive grazing:Evasive grazing: no prevention of no prevention of pasture contaminationpasture contamination as infected as infected animals are turnedanimals are turned--out to pasture; aims to move animals to out to pasture; aims to move animals to ““safesafe””pasture/s before it becomes dangerously infective. pasture/s before it becomes dangerously infective. -- Viable dose & move strategy Viable dose & move strategy onlyonly in young animals (lambs/calves)in young animals (lambs/calves)

Diluted grazing:Diluted grazing: concurrent or alternate grazing of susceptible concurrent or alternate grazing of susceptible (young) animals with resistant/immune (older) animals of the sam(young) animals with resistant/immune (older) animals of the same or e or different species; aims to reduce larval intake by susceptible adifferent species; aims to reduce larval intake by susceptible animalsnimals

Nutrition

Good nutritional levels allow animals to increase their ability to withstand parasitic infections

Effects of animal nutrition on GIN parasites

Changes in the animal defencesChanges in the parasite-gut environment

Nutrition ! Nutrition !! Nutrition !!!

Nutrition

Protein supplementation

Mineral nutrients (COWP)

Bioactive forages

Effect of animal nutrition on GIN parasites

Louvandini et al. (2002)

# adult parasites BW (kg)

High Protein diet + P

High Protein diet

Low Protein diet + P

Low Protein diet

slaughtered(17 wks)

11,900

5,450

82.9

83

73.5

75.5

Effect of animal nutrition on GIN parasites

EwesProtein suppl.

5 wks pre-lambing

EwesProtein suppl.

6 wks post-lambing

EwesNo Protein suppl.

Kahn et al. (2003)

Protein supplementation: 3 times/wk

The effect on FEC still present 8 weeks after supplementation ended.

FEC (43%) No FEC reduction

COWP (Copper Oxide Wire Particles)

Background:

• Oxidized copper was developed for treatment of copper deficiencyin sheep; also used in goats.

• COWP retained to the stomach (abomasum) free Cu released increases [Cu] in the abomasal digesta and is then stored in liver.

• Concentration of soluble Cu creates an environment in the stomach that cause the expulsion of parasites (mechanism?)

COWP (Copper Oxide Wire Particles)

Dairy goats - Exp. infected; 2 or 4 g CON (= 3.4 g metallic Cu)

H.contort. T. circum. T. colubr.

Control 301 1083 1016

CON 74 780 862

Reduc. % 75.4 28 15.2

Worm burdens after 28 days of CON treatment

(Chartier et al, 2000)

COWP (Copper Oxide Wire Particles)

Sheep - Naturally infected; 2 g COWP bolus at week 1 & week 6

(Watkins, 2003)

FEC Reduction:

• Weeks 1-4: 68% – 99 %

• Weeks 7-10: 47% – 72 %

Concepts Concepts

•• ResistanceResistance:: the animalthe animal’’s ability to prevent the s ability to prevent the establishment and development of internal parasites establishment and development of internal parasites

•• Moderate heritabilityModerate heritability•• Lower pasture contaminationLower pasture contamination

•• ResilianceResiliance:: the animalthe animal’’s ability to maintain its production s ability to maintain its production levels while withstanding parasitic challenge levels while withstanding parasitic challenge

•• Lower heritability than resistanceLower heritability than resistance•• Will not lower pasture contaminationWill not lower pasture contamination

Three types of genetic variation: Three types of genetic variation:

* Variation between breeds * Variation between breeds * Cross* Cross--breedingbreeding* Variation within breeds* Variation within breeds

Genetics

Genetic resistance

Reduction of establishment of infective larvae (L3) in the animal’s gastrointestinal tract

Reduction of development of L4 to adult parasites.

Eliminates adult parasites

Reduction of egg-laying capacity of adult female parasites

Effects on parasites:

Genetic resistance

Variation between breeds

Red Maassai > Dorper (Baker et al, 1999)

Gulf Coast Native > Suffolk (Bahirathan et al, 2000)

Texel > Suffolk (Good et al, 2006)

Cross-breeding

Border Leicester x Merino > Merino (Donald et al, 1982)

Texel x Romney > Romney (Niezen et al, 1996)

Indicator traits - based on phenotypic measurements

Fecal egg counts (FEC)Haematocrit (PCV)Plasmatic levels of pepsinogenEosinophiliaIgA activity

Genetic markers - based on genetic polymorphisms

Major Histocompatibility Complex (MHC)Interferon gamma locus

Measurement of genetic resistance

Immunity

Vaccines

Potential for using vaccines has been studied for decades, the results are variable.

Research is being conducted into the mechanisms of naturally-acquired immunity to GIN.

Bioactive forages

Nutraceuticals:

- Foods thought to have beneficial effects on health;- Individual chemicals present in common foods and, therefore, may be delivered in a non-drug form

Bioactive forages

CT: secondary plant metabolites, closely associated with plant defence mechanisms towards insects and mammalian herbivores.

Legumes:

Sulla (Hedysarium coronarium)

Lotus or Greater birdsfoot trefoil (L. pedunculatus)

White clover (Trifolium repens)

Birdsfoot trefoil (Lotus corniculatus)

Sainfoin (Onobrychis viciifolia)

Chicory (Cichorium intybus)

(1) CT may have direct ATH properties;

(2) Consumption of CT also related to indirect effects of tannins: reduced ruminal degradation of diet proteins increased flow of digestible proteins in the small intestine (protein supplementation, therefore nutritional impact of CT)

Bioactive forages (cont.)

Mechanisms

Sheep with reduced parasite egg excretion and decreased parasite burdens.► Effect on intestinal parasites but not abomasal (sainfoin, quebracho)► Effect on abomasal parasites but not intestinal (chicory, sulla)

* exp. from turn-out to weaning (July)► Lambs on chicory pasture: 262 g/d …plus reduced FEC until 13 wk-old► Lambs on grass/clover pasture: 219 g/d

Bioactive forages (cont.)

Results

(Athanasiadou et al, 2001, 2004, 2007)

Considerations !!

* Different plant metabolites seems to affect differently the parasites in stomach and intestine > problem in mixed parasites infections.

* Agronomical > choosing plant species or varieties well-adapted to the various local environmental conditions in different climatic regions

* Metabolical > most plant metabolites have also anti-nutritional properties if consumed in excess; need to clearly assess the balance between positive effects and potential negative consequences

The strategic use of CT forages in grazing management could appear as a promising contribution to the control of GIN

Biological control“An ecological method designed by man to lower a pest or parasite population to keep these populations at a non-harmful level using natural living antagonists”

(Grønvold et al. 1996)

Biological control

Duddingtonia flagrans: nematophagous microfungus

Lab and field studiesEurope, Australia, Asia, N.Am. & S.Am.

Efficacy studies Environmental studies

cattle, sheep, goats, horses, pigs

Duddingtonia flagrans

Adhesive hypha Fungal net

Trapped larva

Chlamydospore(resting spore)

Conidia and chlamydospores

Chlamidosporesin faeces

Germination andgrowth of nematoph.fungus(action on nematodefree-living larvae)

Administration offungal material(chlamidospores)

L1L2L3L3 L3V

Administration of chlamydospores Chlamydospores

in feces

Germination & growth = fungal network nematophagous action on nematode larvae

L3 L3

Biological control by means of nematophagous fungi targets the free-living stages of parasitic nematodes in animal faeces, with the purpose of lowering the larval parasitic population on pasture

Preventive control measure

Fungus-fed Control0

5000

10000

15000

20000

25000

30000

No.

of w

orm

s

Field studies - two locations

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17

0

1000

2000

3000

4000

5000

6000

7000

Control

Mid-June October

Fungus-fed

weeks

L3/k

g D

M

(Jackson et al, 2005)

(Fontenot et al, 2003)

Pasture infectivity (L3) around faecal pats andreduction effect of D. flagrans

Year 1 Year 2

Spring Control 11 1017CI3 5 122 (88%) **TA -- 212 (79%) **

Summer Control 296 1548CI3 44 (85%) ** 360 (77) **TA -- 361 (77) **

Early autumn Control 301 2140CI3 35 (85%) ** 427 (80%) **TA -- 456 (79%) **

**: P<0.01

(Fernández et al, 1999)

Clinical level

Economic threshold

Para

site

popu

lati

on d

ensi

ty

Oscillations in the population density of parasitic nematodes

Sub-clinical level

Uncontrolled Controlled

Message to take homeMessage to take home……

“The important point… is not that any specific control method may be unsustainable when

considered in isolation, but that the more choices there are and the more that different controls

are used in combination rather than relying almost solely on anthelmintics, the longer can we eke out

the continued effectiveness of all of them”

(Barger, 1997)