Biology Reference
In-Depth Information
In a study attempting to induce post-weaning diarrhoea by experi-
mental
E. coli
infection in all piglets, those co-infected with
A. suum
and
T.
suis
had markedly softer feces than controls not infected with helminths,
although the induction of diarrhea was not successful.
70
Additionally, the
helminth-infected pigs also had an increased
Campylobacter
spp. excre-
tion level. Lastly,
A. suum
may negatively affect the post-vaccination
immunity against
Mycoplasma hyopneumoniae
, resulting in increased
pathology, which is probably related to interference with the immune
response as this took place after the lung migratory phase.
4
Ascaris suum
induces a classical Th2 response that may modulate or reduce the Th1
response needed for responding to mycoplasms. The impact of this
finding in the context of commercial farming has not been assessed but
will, besides other factors, depend on
A. suum
infection dynamics on each
specific farm, e.g. the time of first acquisition of infection in relation to
vaccination.
IMPACT OF
ASCARIS SUUM
IN OTHER LIVESTOCK
In cattle, several cases of clinical disease and even deaths due to
A.
suum
have been reported, especially in young stock. Seven out of 17
heifers thus developed clinical signs of severe dyspnea, coughing and
forced expiration after turnout on a
A. suum
contaminated pasture, and
two animals eventually died.
71
In a total of three cases, acute respiratory
distress, pneumonia or fatalities were registered 10 days after exposure
either to pig manure in the feed or to pens previously used for pigs.
72
e
74
A sudden reduction in milk yield, respiratory symptoms, and eosino-
philia were observed on two dairy farms after heifers had grazed
pastures fertilized with pig slurry.
75
The animals were tested positive
for
A. suum
antibodies. Only few incidents of mature
A. suum
in cattle
have to our knowledge been described. Numerous worms were found
in the bile duct of one calf on a farm whereas two other calves had 16
and 168 intestinal worms.
76
Based on morphology,
Toxocara vitulorum
was excluded.
Experimental infection studies support the above-mentioned clinical
observations.
A. suum
larvae were thus recovered on day 10
77
p.i. and
days 7
9 p.i. from the lungs of calves infected with embryonated eggs.
78
These findings coincide with the lung symptoms described in the above
case reports. Greenway and McCraw
79
reported dyspnea, coughing, and
increased respiration rates, consistent with atypical interstitial pneu-
monia, as most pronounced 10
e
13 days after a challenge infection in
7-week-old sensitized calves. Interestingly, the first sensitizing dose of
100,000 eggs was not enough to cause pronounced clinical signs. Similar
lung pathology has also been described in yearling cattle that died after
e
