Gi Nematodes Of Sheep 1 & 2

Front 1

Parasitic gastroenteritis (PGE) accounts for ____% of all digestive tract disease reports in sheep.

Back 1

53%

Front 2

Parasitic Gastroenteritis (PGE)

Back 2

Term for disease caused by parasitic nematodes in GIT.

* Disease of grazing livestock

* Predominantly in young stock; adults generally acquire immunity

* Often caused by mixed parasitic infection

Front 3

What are the top three most important disease syndromes caused by sheep GI nematodes in the UK?

Back 3

1. Parasitic gastroenteritis (PGE)

- Ostertagia Teladorsagia (equivalent of ostertagi in cattle)

2. Nematodirus battus

- significant with lamb populations

3. Haemonchosis

Front 4

Major contributing factors to the increasing trends of PGE, nematodirus & haemonchus contortus infections of ovine in the UK?

Back 4

1. Anthelmintic resistance

- Most resistance Benzimidazole > Levamisole > Ivermectins (macrocyclic lactones)

2. Climate change

Front 5

What are the three main parasites of the ovine abomasum?

Back 5

1. Ostertagia teladorsagia

2. Haemonchus

3. Trichostrongylus

* All from TRICHOSTRONGYLOIDEA superfamily.

Front 6

What are the three main parasites of the ovine small intestine?

Back 6

1. Cooperia

2. Nematodirus

3. Trichostrongylus

^ TRICHOSTRONGYLOIDEA superfamily ^

Others: Bunostomum & Strongyloides

Front 7

What is the most important superfamily of nematode pathogens in grazing ruminant?

Back 7

TRICHOSTRONGYLOIDEA

Front 8

Typical life cycle of trichostrongyloidea? Infective stage? PPP?

Back 8

LIFE CYCLE: Direct

INFECTIVE STAGE: L3

PPP: Short, ~21 days

Front 9

What is the equivalent of ostertagia ostertagi of cattle found in ovine?

Back 9

TELADORSAGIA CIRCUMCINCTA

* Similar life cycle, PPP, infective stage & hypobiosis of L4

Front 10

Life cycle of Teladorsagai circumcincta?

Back 10

Similar to that of ostertagia ostertagi (in cattle):

- Adults in abomasum reproduce & eggs released in feces

- Eggs hatch in feces & moult to the infective L3 stage

- Once ingested penetrate the abomasal gland & moult to L4 stage

- L4s may either enter hypobiosis (arrested state in tissue) or become reproductive adults in abomasum (~d18) & perpetuate the cycle.

Front 11

Of the two types of ostertagiosis in ovine, which is most common?

Back 11

Type I Ostertagiosis - MOST COMMON; buildup of larvae in the Summer, which are ingested by newborn lambs & disease signs are seen in the Autumn

Type II = NOT COMMON

Front 12

Clinical signs of Ovine ostertagiosis (teladorsagiosis)?

Back 12

1. Weight loss/failure to gain weight

2. Intermittent diarrhea (less dramatic than in cattle)

3. Appetite loss

Front 13

Pathology of teladorsagia circumcincta (ovine ostertagiosis)?

Back 13

1. Rupture of intracellular junctions of abomasum

2. Destruction of parietal cells = reduced HCl production

3. Increased abomasal pH (2 ->7) = elevated plasma pepsinogen (inability to convert to pepsin due to lower pH

4. Bacterial overgrowth

Front 14

Diagnosis of teladorsagia circumcincta?

Back 14

1. Observation of clinical signs (predominantly in lambs)

2. Monitoring time of year (grazing & anthelmintic history)

3. FEC

4. PM

Front 15

Epidemiology of teladorsagia circumcincta?

Back 15

TYPE I = Sept - Nov infections very high due to Spring born lambs feeding on highly contaminated Summer pasture

Front 16

Worm burdens and FEC low in adult ewes, except during ____________________________.

Back 16

PERIPARTURIENT PERIOD

- Approx 2 weeks before to 6 weeks after lambing

Front 17

Higher worm burdens in ewes during periparturient period (2 wks before to 6 wks after lambing) is due to:

Back 17

1. Increased establishment of overwintered larvae acquired from pasture

2. Inhibited L4s within tissue reactivating & developing to adults

3. Female worms have increased fecundity due to plumpness of pregnant ewes

Front 18

What is the main difference in epidemiology between bovine and ovine ostertagiosis?

Back 18

Ewes are the main source of egg contamination to pasture, shedding large amounts during their periparturient period (Spring months: Feb-April)

- Lambs are then exposed to these freshly excreted eggs along with overwintered larvae during Summer months, resulting in large amounts of infective L3 on pasture from about late-July to Oct

Front 19

Control methods of ovine ostertagiosis (teladorsagia circumcincta)?

Back 19

1. NOT GRAZING HEAVILY-INFESTED PASTURE with susceptible lambs

* Rotate pastures

2. Anthelmintic treatment of ewes & lambs!

* Resistance is a major problem

Front 20

What is the largest parasite in the abomasum of the sheep?

Back 20

HAEMONCHUS CONTORTUS

"Barber's pole worm"

Blood sucking worm, which causes haemorrhagic anemia (>5000 adult worms can have very serious if not fatal effects)

Front 21

Extremely pathogenic nematode (poor immunity) that is of major concern in tropical climates, but causes only sporadic disease in temperate climates.

- Anthelmintic resistance common

- "Model parasite" for research

Back 21

HAEMONCHUS CONTORTUS

Front 22

Life cycle of Haemonchus contortus?

Back 22

Typical trichostrongylid:
- Eggs shed in feces

- Within feces, eggs moult to infective L3 stage (2-12 weeks depending on climate)

- Infective L3s ingested from contaminated pasture into host (ruminants)

- Continue development within host to adults who live within the abomasum, suck blood & reproduce

Front 23

Sheep may develop complete immunity to Haemonchus contortus.

True or False?

Back 23

FALSE - Ewes remain susceptible to disease

Front 24

Pathogenesis of ovine haemonchosis can be broken into three different categories. What are they & list clinical signs?

Back 24

1. Hyperacute Haemonchosis (up to 30,000 adults)

- Sudden death due to severe haemorrhagic gastritis

2. Acute Haemonchosis (2,000-20,000 adults)

- Clinical signs seen ~2 weeks post-infection

- Regenerative anemia followed by non-regenerative if not treated

- Submandibular edema, ascites (fluid build-up) dark feces (blood loss), dropping wool, inappetance

3. Chronic Haemonchosis (several hundred)

- Weight loss, weakness & inappetance

- Anemia absent or slight

Front 25

Bottle jaw is a clinical sign of nematodes that effect the abomasum.

True or False?

Back 25

TRUE = submandibular edema!

Front 26

Diagnosis of Haemonchosis?

Back 26

1. Observation of clinical signs

- Anemia = pale mucous membranes

- Ewes & lambs both affected

- Predominantly, dense lowland flocks

2. FEC (Fecal egg counts); very fecund!

- Typical trichostrongyle egg

- 1,000-20,000 epg

3. Post-mortem

- Large, 2-3cm worms on lumenal surface of abomasum; appear dark brown

Front 27

FAMACHA?

Back 27

System for assessing clinical anemia, based on conjunctiva color of the eye.

- Used to decide which animals in a flock to treat

- Increasingly used in tropical countries

- Five different levels: 1-2 (no dose), 3 (borderline), 4-5 (dose!)

Front 28

Epidemiology of haemonchus contortus?

Back 28

Best adapted to warm climates, as larval development in environment requires high temps & humidity.

Epidemiology varies depending on region:

1. Tropical with little/no dry season (E. Africa)

- High burden year round = year round anthelmintic usage

- High worm fecundity

- # of L3s on pasture dependent on rainfall

2. Tropical with severe dry season (AU, Brazil)

- L3 don't survive dry season

- High levels of inhibited larval development; parasite survives predominantly in host

- Disease outbreaks at start of wet season due to reactivation of inhibited L4s & rapid inc in pasture L3s

3. Temperate (UK, W Europe)

- Inhibited L4s reactivate in Spring, leading to pasture contamination of infective L3s in Summer (May-Aug)

- Lambs ingest these Summer L3s & lead to outbreaks in Autumn (Sept-Nov)

- Almost 100% of larvae ingested in October-on will become arrested in tissue until following Spring.

Front 29

Nematodes of sheep small intestine?

Back 29

Trichostrongyloidea (superfamily):

1. Nematodirus

2. Trichostrongylus

3. Cooperia

Strongyloidea Bunostomum

Front 30

"Cotton wool worm"

- Major cause of specific syndrome in lambs in the UK

- Epidemiology different to other causes of PGE (Spring)

Back 30

NEMATODIRUS BATTUS

Front 31

Life cycle of NEMATODIRUS BATTUS?

Back 31

Similar to that of other trichostonglyoidea species as far as egg excretion in feces & ingestion of infective L3s from pasture.

BUT MAJOR DIFFERENCE:

- L1-L3 development within the environment occurs WITHIN THE EGG, then larvae remains inactive while overwintering for 8-9 months before hatching in the SPRING and being ingested.

Front 32

Describe the very specific hatching requirements of nematodirus battus, which make this trichostrongyliodea parasite life cycle different from the rest.

Back 32

Requires prolonged period of chill followed by a mean day/night temperature of 10C

Front 33

Lambs more than _______ of age are non-permissive hosts of nematodirus battus.

Back 33

>3 months of age

* Ewes very resistant to infection; no periparturient rise unlike in telodarsagia circumcincta

* Resistance is physiological & not due to acquired immunity

Front 34

Lambs between the age of ____________________ are susceptible to nematodirus battus.

Back 34

between 3 weeks - 3 months

* Lambs don't graze significantly during first few weeks of life & after 3 months have acquired physiological resistance.

* For disease to occur emergence of L3s must coincide with presence of susceptible lambs

Front 35

Pre-Patent Period (PPP) of nematidorus battus?

Back 35

TWO WEEKS (very short)

Front 36

During what time of the year are nematodirosis diagnoses highest in the UK?

Back 36

Summer months

* Scotland = May-July

* Wales/SW England = April-July

Front 37

Ewes play little role in epidemiology of nematodirus battus.

True or False?

Back 37

FALSE - Ewes develop age resistance; "lamb-to-lamb" disease

* Large #s of L3s hatch in Spring from eggs passed onto pasture from last years lambs

* Unlike, telodarsagia circumcincta where ewes experience periparturient rise in fecal egg release, contributing massively to epidemiology.

Front 38

Risk of outbreaks of nematodirus battus varies from year to year on particular farms depending on __________ & ______________.

Back 38

CLIMATE & LAMBING PERIOD

Front 39

______________ are permissive hosts of Nematodirus battus.

Back 39

CATTLE - particularly young calves; disease occasionally occurs in calves

* Consideration in rotational grazing

Front 40

Pathogenesis of nematodirus battus?

Back 40

- Pathology largely due to larval stages, which cause severe disruption of SI mucosa

- Most damage = 10-12d post-infection (L4-adult moult

* Can be severe if L4s reactivated at same time as newly acquired L3s moult.

- Results in enteritis & villus atrophy

Front 41

Clinical signs of nematodirus battus?

Back 41

RAPID ONSET (10-12 days)

- Profuse diarrhea

- Dehydration (increased thirst)

- Lambs severely affected & can die quite rapidly if arrested L4s reactivated at same time as newly acquired moulting L3s.

Front 42

Diagnosis of nematodirus battus?

Back 42

1. Grazing history

2. Clinical signs (profuse diarrhea, dehydration, inc thirst)

3. PM - cotton wool worms in SI

* Fecal egg counts not reliable since pathology often due to larvae

Front 43

Control of nematodirus battus?

Back 43

ROTATIONAL GRAZING

- Avoid grazing ewes & lambs on pasture used for lambs the previous year (ideally previous two years)

Front 44

What is distinctive of the nematodirus battus egg compared to the teladorsagia & other trichostrongyloidea species?

Back 44

Distinctive parallel sides with several blastomeres observed within.

- LARGER

Front 45

What are the three main trichostrongylus species of parasites found in ovine SI?

Back 45

TRICHOSTRONGYLUS:

1. vitrinus (black scour worms) = sheep & goats

2. capricola = sheep & goats

3. colubriformis = all ruminants

Front 46

Commonly contributes to PGE in lambs in Autumn/early Winter, resulting in dark, foul smelling, mucousy feces.

- Causes chronic wasting disease in hoggs & ewes in early Winter

- Poor skeletal growth & wool quality

Back 46

Trichostrongylosis

Front 47

Epidemiology of trichostrongylus vitrinus is similar to that of T. circumcinta, except tends to occur _________ in grazing season.

Back 47

LATER (Sept-Dec/Jan)

Front 48

Pathology of Trichostrongylosis?

Back 48

Larvae & adults burrow beneath the surface epithelium resulting in:

- Enteritis

- Mucous & mucousal hypertrophy

- Lamina propria infiltrated with inflammatory cells

- Villi shortened/atrophy

- Lesions become more localized as resistance develops = "finger-print" lesions

Front 49

Cooperia curticei infects the ___________ of sheep, is not very pathogenic, but is a _______________ species, meaning it requires increased amounts of anthelmintics & underdosing can commonly lead to resistance.

Back 49

SMALL INTESTINES

DOSE-LIMITING SPECIES

Front 50

Life cycle of cooperia curticei?

Back 50

Typical trichostrongyloidea life cycle!

- Eggs shed in feces

- Moult to infective L3 stage

- Ingested by host

- Moult to adults in host & reproduce

Front 51

Small intestinal parasite with large bursa that grow to be ~1 cm and have "watch spring" appearance.

- Not very pathogenic

- Dose-limiting species

Back 51

COOPERIA CURTICEI

Front 52

Sheep & goat hookworm found in the SI

- Superfamily Strongyloidea

- Adults 1-3 cm w/ hooked anterior end & cutting plates which bite off chunks of tissue & feed on blood

- PPP = 1-2 months

Back 52

BUNOSTOMUM TRIGONOCEPHALUM

Front 53

Life cycle of BUNOSTOMUM TRIGONOCEPHALUM?

Back 53

Typical hookworm life cycle:

- Eggs released in feces

- Infective L3s picked up either percutaneous route with pulmonary migration or orally (ingested)

Front 54

Nematodes of the sheep LI?

Back 54

STRONGYLOIDEAs:

1. Chabertia ovina = large-mouthed bowel worm

2. Oesophagostomum spp

TRICHUROIDEA:

1. Trichuris ovis

Front 55

Large-mouthed bowel worm of LI

-1.5-2cm with large buccal capsule

- No cutting plates, but removes chunks of mucosa

- Common in temperate regions, but disease important during warmer, Winter rainfall areas (AU & S. Africa)

- Low levels of infection

- Contributes to PGE

Back 55

CHABERTIA OVINA (Strongyloidea)

Front 56

Life cycle of Chabertia ovina?

Back 56

1. Adults in colon release eggs into feces

2. Eggs moult to infective L3 stage

3. L3s ingested & enter SI or LI mucosa

4. Moult to L4 at ~1 week

5. L4s may either emerge & migrate to cecum and eventually colon or arrest until environmental conditions are ideal

Front 57

Pathogenesis of chabertia ovina?

Back 57

CONTRIBUTES TO PGE (parasitic gastroenteritis)!

- Mucosal damage

- Hemorrhage

- Protein losing enteropathy

- Diarrhea

- +/- anemia

* 200-300 worms cause disease!

Front 58

What are the oesophagostomum species commonly found in sheep?

Back 58

1. Oesophagostomum columbianum = nodule formation

2. O. venulosum = no nodule formation

Front 59

Large bowel worm whose L3 migrates into the tissue triggering an immune response by the host & causing nodules.

Back 59

Oesophagostomum columbianum

Front 60

Clinical signs associated with oesophagostomum species?

Back 60

Diarrhea & weight loss

* Clinical signs unusual in UK.

Front 61

What are the top three ovine PGE contributors in the UK?

Back 61

1. Telodorsagia circumcincta = Abomasum

2. Trichostrongylus vitrinus = abomasum & SI

3. Nematodirus battus = SI of Spring lambs!

Front 62

__________ intestine ovine parasites are typically present in small numbers.

Back 62

LARGE intestine parasites present in small numbers.

Front 63

Goats generally have problems with the same parasites that infect sheep, but goats are _______ susceptible. Why?

Back 63

MORE - Because goats are naturally browsing animals, which are often forced to graze. So less adapted/immune than sheep to grazing parasites.

Front 64

How does anthelmintic treatment for goats differ from that of sheep?

Back 64

Control more difficult for goats

- Anthelmintics used on ALL AGE GROUPS & often MOST OF THE YEAR.

- Pharmacokinetics differ; Goats require 2X the dosage (underdosing common)

- Resistance develops much more quickly.

Front 65

Fecal egg counts and adult worm burdens have a linear relationship.

True or False?

Back 65

FALSE - NOT LINEAR; too many varying factors per individual, such as:

- # of adult parasites present

- level of host immunity

- age

- species of parasite

- stage of infection

- consistency of feces

Front 66

Give two examples of disease syndromes which are caused by pre-patent parasites (before eggs are present in feces):

Back 66

1. Type II Ostertagiosis in Cattle

2. Nematodrus battus

Front 67

What are two major guidelines for accurate FEC samplings?

Back 67

1. Sample sufficient number of animals per group

- At least 10 animals for large groups

- All in small groups

2. Sample from a mixture of severely affected, moderately affected & clinically normal animals.

Front 68

FEC general rules of thumb for diagnosis for:

1. Teladorsagia/ostertagia

2. Haemonchosis

3. Nematodirus

Back 68

1. Teladorsagia:

- 200 epg = burden to sufficient

- 200-1000 epg = mild/moderate clinical signs

- >1000 epg = HEAVY BURDEN

2. Haemonchosis

- 1000-2000 epg often seen

3. Nematodirus

- FEC often low or even -ve with significant worm burdens