Page 65 - The Welfare of Cattle

42 the WeLfare of CattLe

table 6.3 Immature Development habitat for Cattle ectoparasites
Fresh Manure & Manure-
Cattle Cattle Pen Cattle Fermenting Polluted Other
Cattle ectoparasites Body or Pasture Feces Feed Ponds aquatic
Lice x
scabies or “mange” mites x
new World screwworm fly x x
(Cochliomyia hominivorax)
Cattle grub (Hypoderma spp.) x x
spinose ear tick (Otobius megnini) x x
Cattle fever ticks (Rhipicephalus spp.) x
3-host ticks (e.g., Dermacentor, x
Amblyomma ticks)
Pajaroello tick (Ornithodoros x
coriaceus)
horn fly (Haematobia irritans) x
stable fly (Stomoxys calcitrans) x
horse and deer flies x
biting midges (Culicoides spp.) x x
black flies x
Mosquitoes x x
face fly (Musca autumnalis) x
house fly (Musca domestica) x

determines the abundance and likely impact of these biting flies. However, the greater cattle density
in intensive operations may actually decrease damage and disturbance caused by these biting flies
as the number of bites received by any individual animal would be reduced.
Some biting midges (e.g., Culicoides sonorensis) and some mosquito species are more abundant
in aquatic habitats with high concentrations of animal feces or other organic pollutants. These spe-
cies can be quite abundant in intensive systems, particularly where manure-polluted wastewater is
accumulated in poorly designed storage systems. Increasing abundance of Culicoides is associated
with increasing transmission of bluetongue virus to cattle. Pasture systems are expected to have rel-
atively low numbers of the biting midges and mosquitoes that develop in polluted aquatic habitats,
but only if animals and their fecal waste are excluded from any aquatic habitats on or near pastures.
For ectoparasite species that must spend at least part of their life off the host, survival is greatly
influenced by habitat characteristics associated with the production system. While ectoparasites
are off the host and on the ground, they are subject to mortality from unsuitable environmental
conditions. Pasture vegetation provides refuge from direct sunlight, high temperatures, low humid-
ity, and dusty conditions. In contrast, dry dirt pens typical of intensive systems offer little refuge.
Ectoparasites that drop from animals in an intensive system may have to crawl or wriggle very far
indeed to reach a shaded area. Perhaps of equal importance for survival is the likelihood of being
squashed beneath the hooves of your host. In pasture systems, ectoparasites have little risk of being
stepped on as cattle density in these systems is relatively low. While in intensive systems where
cattle density is high, it must be quite a wild race across the busy pen for an unfortunate ectoparasite
that drops from its host near the middle of the pen! One might consider the risk to ectoparasites from
predators (e.g., ants, spiders, lizards, rodents) to be higher in pastures than in dry pens, but this risk
is probably minor relative to the other factors that affect off-host survival.
An additional aspect of ectoparasite survival must be considered for ticks that require blood
meals from non-cattle hosts during their immature stages. Most 3-host ticks commonly require