Biology Reference
In-Depth Information
helminthosis in general ranks within the 10 most important pathogens
worldwide.
1
And even though industralized in-door production with
high levels of hygiene may have lower prevalence than more traditional
systems,
2
recently implemented changes in management to accommodate
for better welfare, i.e. group housing of dry sows (
non-lactating, most
often pregnant sows) and sprinklers as a surrogate for wallowing, may
increase the prevalence within these herds.
3
This chapter will try to describe the impact of
A. suum
by revisiting
some of the older controlled experiments and review some more recent
studies under farming conditions, and examine if there is a quantitative
relationship between worm load and pathogenicity. Nodular worms
(
Oesophagostomum
spp.) and numerous other worms are commonly
encountered co-infections to
A. suum
in pigs, particularly in natural
settings and outdoor systems.
2
Understandably, effects of
A. suum
are
difficult or impossible to single out from combined effects of these
multiple parasite infections but data will nevertheless be used when
relevant.
This chapter will examine the direct effects on health (clinical and
subclinical effects) and performance (subclinical effects). It is evident that
the underlying pathophysiological changes and thus impact will depend
on level of exposure (dose level in experimental infections), stage of
infection, build-up or maintenance of immunity, nutritional and physio-
logical status, and possible other factors. Indirect effects on susceptibility
to bacterial and viral infections or enhanced pathogenicity, related to, for
example, the lung migratory phase or immunomodulatory capacity of
A. suum
,
4
will be summarized although the mechanisms behind the latter
phenomenon are thoroughly addressed in Chapter 4. Focus will be on the
natural host, the pig, but the chapter will also examine implications of
A. suum
in other livestock.
¼
ASCARIS SUUM
AND OTHER HELMINTHS IN PIG
PRODUCTION SYSTEMS
The most important intestinal helminth fauna of pigs in Europe and
other temperate regions includes nematodes like
Strongyloides ransomi
(mainly in suckling piglets
¼
piglets in the suckling phase (4
e
10 weeks
of age depending on production type)),
2
A. suum
(fatteners
¼
growing
finisher)),
2
Tr i c hu r i s s u i s
(fatteners),
2
Oesophagostomum
spp. (adult pigs: sows and
boars),
2
Hyostrongylus rubidus
(sows and boars),
2
and
Globocephalus
urosubulatus
(rarely found)
5,6
while spiruroid nematodes (e.g.
Ascarops
strongylina
,
Physocephalus sexalatus
)
5,7
are also commonly found in
warmer parts of the world.
Oesophagostomum dentatum
is overall the
¼
pigs after weaning up to time of slaughter (large fattener
