Nematodes of sheep Flashcards
Nematodes typically have what kind of life cycle
Direct life cycle
Nematodes typically have what requirements for environmental stages
Warm and moist
Nematodes typically have what clinical signs
weight loss and diarrhoea
Most notable clinical sign of Parasitic Gastroenteritis (PGE)
Reduced weight gain
Reduced feed intake (60-70% of reduced DLWG)
Cause of clinical signs of Parasitic Gastroenteritis (PGE)
Both developing larvae and adult GI nematodes can cause damage to the mucosal lining of the GIT, leading to discomfort, anorexia and malabsorption, which can be prolonged if the damage is long term
Describe distribution of infection for nematodes in sheep
generally over-dispersed, with only few sheep carrying heavy worm burdens, whilst the majority of sheep carry low numbers of worms
Parasitic Gastroenteritis (PGE)- Diagnosis
Reduced growth rate (in absence of other ddx)
Faecal worm egg count
Post mortem examination
FAMACHA
What is the name of technique used in faecal worm egg count
McMaster
Dilute faeces then multiply result
Give eggs per gram (epg)
Nematodirus species are the exception with eggs that look different, much _________ and ___________than the Trichostrongylids, with _______________inside of them
larger and darker
large brown balls visible inside of them
Pro of faecal worm egg count
Predict pasture contamination
Determine pattern of infection on individual farms
Encourage farmer/vet interaction
Fecal Egg Count Reduction Test
Nematodirus battus diagnosis
Cons of faecal worm egg count
Cannot speciate Trichostrongyle style eggs
FWEC not representative of burden (except H. contortus)
Not related to lamb performance (resilience vs resistance)
Parasitic Gastroenteritis (PGE)- Diagnosis
post mortem examination
H. contortus- Treatment
Closantel and Nitroxynil
Nematodirus battus- Treatment
Benzimidazoles (BZ)
What period of time to administer antihelminthics
Autumn to kill hypobiotic larvae
Hypobiosis
Arrested development
Species that typically go hypobiosis
HaemonchusandTeladorsagia
Why do species go hypobiosis
Under unfavourable conditions, such as autumn in temperate climates like the UK or hot dry conditions in other countries
Peri-parturient rise (PPR)
These infections produce more eggs because of the reduction in immune response in late pregnancy and early lactation, more nematodes develop and the rate of egg shedding is increased
Outline main ways of reducing pasture contamination by ewes during the peripaturient rise
Supporting the ewes to have a good immune response by good nutrition, breeding replacements from ewes with low FWEC, providing clean grazing for ewes and giving lambing ewes anthelmintic treatments during the period of highest egg shedding.
Vaccine for Haemonchus contortus (Barber pole worm)
Barbervax
Problem with ‘Dose and move’ protocol in the past
Treat lambs with anthelmintic at the time that they are moved to clean grazing (pasture with low larval contamination). However this promotes resistance development because the resistant ones are the only nematodes that will survive treatment and then be deposited on the clean grazing.
GIN that resides in abomasum
Teladorsagia circumcincta the ‘brown stomach worm’
Haemonchus contortus the ‘barber’s pole worm’
GIN that resides in small intestine
Trichostrongylus vitrinus ‘black scour worm’
Trichostrongylus colubriformis ‘black scour worm’
Nematodirus battus
Has different epidemiology to other nematodes
Clinical sign of Teladorsagia circumcincta (brown stomach worm) and time of year
Scour, loss of appetite and weight
Summer
Clinical sign of Trichostrongylus species (black scour worm) and time of year
Dark scour, anorexia, poor skeletal growth, chronic ill thrift
Late summer, autumn and/or winter
Does Haemonchus contortus cause diarrhoea
No
Outline how Nematodirus battus has a different epidaemiology
development of its environmental stages progresses more slowly (taking several months) and mostly occurs while contained within the egg. Once the larvae have reached L2, they are able to hatch and moult immediately to the infective L3,
Nematodirus battus- Treatment
Benzimidazoles
