Parasitic Gastroenteritis (PGE)

What causes parasitic gastroenteritis?

Trichostrongyles

What type of parasite are trichostrongyles?

Nematodes

Prevalence of trichostrongyles

• Ubiquitous in the environment

• Grazing animals will be infected at least once in their lives

• Most common parasite of grazing animals

Which animals do trichostrongyles cause disease in ?

• Hosts with no protective immunity

• Young animals

• Older animals who have not been previously infected

• Causes disease in hosts with other illnesses and/or stressors

• Rarely zoonotic

Life cycle and transmission of trichostrongyles

• Direct- host ingests infective larvae (feces)

• Transmissible between different ruminant species

Name of trichostrongyles in cattle

Ostertagia ostertagi (brown stomach worm)

Trichostrongyles in sheep/goats

Haemonchus contortus (barber pole worm)

What site do trichostrongyles infect in ruminants?

Small intestine

Types of trichostrongyle infections

• Orchestra (usually)

• Soloists

Consequences of trichostrongyle infection

• No effect

• Sub-clinical: production losses but no obvious signs of disease, decreased appetite, rough coat

• Clinical disease (PGE): Can be debilitating or fatal, burden of parasites, typically only a few animals in a herd

Clinical disease caused by Haemonchus

• Soloist infection

• Anemia (blood sucking parasites)

• Edema

Clinical disease caused by Ostertagia

• Soloist infection

• Diarrhea

• Emaciation

• Anemia

• Low blood protein

Diagnosis of trichostrongyle infection

• Infection more common than disease

• Fecal sample identifies infection but not disease

• Eggs cannot be differentiated morphologically

Diagnosing PGE

• Qualitative centrifugal fecal flotation

• Quantitative fecal flotation

• Blood work

• Identifying worm genus

• Postmortem exam

Management of PGE

• Biosecurity

• Monitoring for signs of disease

• Occasional treatment with anthelmintics

• Refugia principle

• Preventing infection/disease

• Quarantine

• Alternative (non drug) options

Prevention

• Provide adequate nutrition to host

• Mitigate stressors in host

• Disrupt life cycle of agent

• Avoid overgrazing

• Let contaminated pastures rest

Monitoring

• Body condition scoring

• Track production metrics

• FAMACHA

Treatment

Anthelmintics/dewormers- occasionally

What is a refugium?

A proportion of worms that as never been treated with anthelmintics- retain alleles in the worm population that confer susceptibility to anthelmintics