Lecture 1: ectoparasites of ruminants Flashcards
Why is production animal health important?
- Economical advantages
- Management of disease in an economic way is crucial
- animal health relates directly to welfare: Production, ethics and marketing/public perception
Definition of health
Health is a state of complete well-being and not merely the absence of disease, the animal has to be holistically healthy, not merely the absence of parasite and disease
define productivity
A healthy animal grows, reproduces and behaves in a manner which has come to be regarded as normal for its species and type
Classification of disease
- Clinical sign: Acute diarrhea
- Set of clinical signs (syndrome): Sudden death in cattle
- Anatomical abnormality: deformed cattle
- By “Cause”: Clostridial disease in cattle
Factors in an epidemiological triad
And explain their relationship
Host, agent and environment
These factors are all interlinked, its rare that one particular outcome will be caused by one factor, there will be multi-factorial things involved
All diseases are multi-factorial
How to detect disease
Clinical disease (Overt signs):
- Animals are dull, less responsive
- Rough coat, poor body condition
- Discharge, coughing, increased respiratory rate
- Diarrhea (Scours)
- Swelling
Subclinical disease (No overt signs) 1. Very mild form of disease 2. Decreased production 3. May be carriers of infectious agents Harder to pick up, look ok but not ok as there are no obvious signs
Why are subclinical disease important?
it can be the tip of the iceburg as nothing is full blown yet, if it is detected it can be treated early and prevent loses in production and death
preventing infection from spreading
If missed, it will turn from subclinical to clinical
Cost of disease
Production losses welfare impact public perception biosecurity occupational health and safety
Cost of controlling disease
Treatment costs
cost of culling
Prevention cost: How to protect farms around infected farms and how to manage (bio-security)
What do we choose to control:
Host - change genetics to make animals more parasite resistant
Agent
Environment: If too got sheep parasite can change to cows
Factors that affect animal production health and welfare
Genetics Nutrition: Feed quality and availability Seasonal variations (Climate, drought) Disease Cost of control measures (Labour and treatment)
Complex/indirect lifecycle vs direct lifecycle of parasite
A parasite that must infect more than one host species to complete its lifecycle is said to have a complex or indirect life cycle
A parasite that infects only one host is said to have a direct lifecycle
Facultative parasites
An organism that lives independent of a host (Free living) but may occasionally be parasitic under certain conditions
Obligate parasites
an organism that cannot complete its lifecycle without exploiting a suitable host
Host classification
Definitive host: A host that harbors a parasite while the parasite reproduces sexually
Intermediate host: A host that harbors a parasite during some of its developmental stages
Natural host: A host that is naturally infected with a certain species of a parasite
Accidental host: A host that is not normally infected with a particular parasite
Host interaction
Symbiosis
Mutualism
Commensalism: One benefit other unaffected
Parasitism: A relationship between 2 organisms where one benefits at the expense of the other
Parasite classification
- Protozoans
- Helminths: Nemathelminthes, Platyhelminthes
- Arthropods
Arthropod characteristics
Have cuticle to keep foreign substances from entering and also helps control fluid loss *Dessication”
HAve muscles
Circulatory system called the haemocoel, no veins or arteries
Have a brain called the oesophageal ganglion: Where all the nerves and neuron comes together
Insecticides works to target their neurotransmitter (Over excite or block the nervous system)
Ach (acetylcholine estrase) GABA (Gamma-aminobutyric acid)
Respiratory system: Tracheal system (terrestrial arthropods) and spiracles (external respiratory opening)
Arthropod life cycles key features
Sexes are separate
moulting takes place
different stages are called instars
Metamorphosis are common
Orders of insectas
Diptera - wings
Siphonapetara - no wings
Phthiraptera - no wings
classification of Diptera
Nematocera
Brachycera
Cyclorrhapha: True flies - breeds in vegetable or animal material both living and dead
Classified based on their antennae and wing shape
Oestrus ovis
Order: Diptera Family oestridae Nasal bot of sheep and goat -fly viviparous (lays larvae not eggs on external nares) -Larvae crawls into nasal cavity -third instar sneezed out -pupae develop in soil -flies are active in summer
Effect on sheep:
Agitates sheep when laying larvae
Chronic nasal discharge
Predisposes to pneumonia (Not common): maggots dont cause pneumonia but the discharge can attract other insects and bacteria
Treatment: Organophosphates Macrocycle lactones Trematocides May be zoonotic occasionally
Muscidae
Order: Diptera
Life cycle: Fly > egg > Larvae (3instars) Pupae > Fly
Subfamily muscinae
House fly: Musca domestica
Breed in dung
non-biting
Nuisance
can induce nasal scold and dermatitis around the eye of cattle of horses
Control: Manure management, parasitic wasps, predatory mites, baits, raps and sprays
Bush fly: Musca vetustissima
Overwinter in north Australia (dont like cold)
Nuisance, non-biting
same problem as M. domestica
dung beetle is a key component in the fight against bush flies
Remove cow pads in feed lots (Dung)
Subfamily Stomoxinae Stable fly: Stomoxys calcitrans Breed in decaying organic matter Feeds on blood, mainly cattle both sexes feed on blood bites anything Negative impact on productivity (PEST) Affects productivity by taking animal away from feeding and growing, the animals will be busy finding a place to get rid of pest
Buffalo fly: Haematobia exigua Small grey fly Rigid biting mouthparts Introduced in SEA Feeds on cattle dairy and beef
Haematobia exigua life cycle
Features: Direct lifecycle Flies remain on host Dies in 1-2 days away from host leave host to lay eggs breeds in cow dung Emerging flies have 1-2 hours to find host need blood meal to breed adults live for 10-20 days need temperature >20oC Life cycles takes 7-11 days
Epidemiology: Spread by travelling cattle up to 7km
geographical distribution limited by temperature and moisture
Effect on host: painful bites Cattle rub to relieve irritation 2000-3000 flies for heavy infection loss of condition or delay infattening milk production drop
Vector of Trypanosoma evansi
vector of filarial nematode (Causes skin lesions (Dermatitis) Downgrading of hide quality and welfare
Costs 100 million dollars Controls: Fly traps (tunnel trap) Ear tags impregnated with insectides Ivermectin (Insecticide that persists in dung, but will kill dung beetle) dung beetles integrated control OP sprays
Melophagus ovinus
Sheep ked: No wings Lives in wool Females are viviparous Pupal case attached to wool pupae hatch in 19-36 days Adults emerges and feeds Adults can live for 4-6 months Mainly winter pest
Effect on host:
Blood feeders, bites repeatedly, irritation
causes anaemia
stain wool (Ticky wool)
Transmits Trypanosoma melophagium (Non-pathogenic protozoa)
Treatment:
Dips or sprays containing ivermectin, organophosphates, pyrethrin and rotenone
Follow up treatments 3-4 weeks later is recommended due to the length of time of the pupal stage
Management: Shear ewes (female lambs) prior to lambing which should remove 75% or more of the kids
reduces contamination from dam to new born lamb
