Localization of Trichinella spiralis in muscles of commercial and

Article available at http://www.parasite-journal.org or http://dx.doi.org/10.1051/parasite/200108s2246
LOCALIZATION OF TRICHINELLA SPIRALIS IN MUSCLES
OF COMMERCIAL AND PARASITOLOGIC INTEREST IN PORK
RIBICICH M., MIGUEZ M., ARGIBAY T., BASSO N. & FRANCO A.*
Summary:
Trichinellosis is widespread around the world with different
representatives of the genus Trichinella found in almost every
continent. In Argentina the main source of transmission for the
disease to humans is pig meat infected with Trichinella spiralis.
The object of this work was to determine the distribution of
Trichinella larvae in fresh meat cuts which are sold for human
consumption and in the muscles traditionally used for the disease
diagnosis at meat-packing plants. Cranial muscles to the last rib
showed more Trichinella spiralis larvae than those with a caudal
location (p < 0.01). No significant differences were found
(p > 0 . 0 5 ) between bilateral left and right muscles. Significant
larval concentrations were found in the neck muscles, even in
carcasses with a low parasitic load; these muscles are used to
prepare cold meats (boston butt). Commercial cuts of meat had a
substantial larval burdens in animals experimentally infected with
5 0 0 to 5 , 0 0 0 Trichinella spiralis larvae, with parasite burdens
similar to infection levels in muscles evaluated at the meat packing
plant.
MATERIALS AND METHODS
PIG
INFECTION
T
h e w o r k w a s carried out with 14 c o m m e r c i a l
hybrid pigs, Landrace a n d Large White crossbred, originating from a cattle-breeding ranch in
the province o f B u e n o s Aires. T h e y w e r e 6 0 days old
at t h e b e g i n n i n g
o f the experiment
and weighed
approximately 20 kg e a c h . All animal w o r k w a s perf o r m e d in the swine breeding facility b e l o n g i n g to the
Faculty o f Veterinary S c i e n c e s at the University o f
B u e n o s Aires. T h e parasite
Trichinella
spiralis
was
m a i n t a i n e d b y serial p a s s a g e in f e m a l e CF-I m i c e
o b t a i n e d from the Department o f Parasitology, ANLIS.
Dr. Carlos G. Malbrán, Argentina.
Muscle larvae w e r e r e c o v e r e d from m i c e b y acid-
KEY WORDS : Trichinella spiralis, pigs, meat inspection.
pepsin digestion o f striated m u s c l e c o l l e c t e d at least
3 0 days after infection.
I
Pigs w e r e orally inoculated with infective larvae o f Trin Argentina the main source o f transmission o f tri-
chinella
chinellosis to humans is pig meat infected with Tri-
cator bolus-flowing gun. T h e pigs w e r e experimentally
chinella
inoculated with d o s e s o f 100 (group 1), 5 0 0 (group 2 ) ,
spiralis.
The muscles where
Trichinella
spiralis
larvae esta-
blish vary according to the host ( G o u l d et al., 1970;
Campbell et al., 1 9 9 3 ; Reina et al,
1994;
Pozio
et al.,
slaughter i n s p e c t i o n
using a Coopers® Cattle pellet appli-
5,000 (group 3 ) or 5 0 , 0 0 0 (group 4 ) larvae o f
nella
Trichi-
spiralis.
1996; Kapel et al.,
1998). The muscles
for Trichinella
spiralis
used for
infection
(dia-
phragm, tongue, masetters, intercostals) are t h o s e that
contain the highest n u m b e r o f larvae p e r gram (Kotula
et al., 1 9 8 4 ; Zimmerman et al., 1 9 7 0 ) . T h e objective o f
this w o r k w a s to determine the distribution o f larvae
o f fresh meat cuts which are sold for human c o n s u m p tion and in the muscles traditionally used for inspection in meat-packing plants.
TISSUE
RECOVERY
On day 100 post-inoculation, all 14 pigs were sedated
and euthanized by exsanguination. Following euthanasia, the animals were eviscerated and tongue muscle,
tongue base, masseters, diaphragm, intercostals and commercial cuts such as ham, shoulder, boston butt, fillet,
spare ribs and belly were collected for artificial digestion.
DIGESTION
TESTING
Distribution o f T. spiralis
larvae in e a c h tissue s a m p l e
w a s determined b y digestion o f 100 g o f tissue ( G a m ble, 1 9 9 6 ) .
STATISTICAL
ANALYSIS
* Faculty of Veterinary Sciences. University of Buenos Aires, Chorroarin 280 (1427) Argentina.
Correspondence: Mabel Ribicich.
Tel.: 54-11-4580-2820 - Fax: 54-11-4514-8962.
A test for proportion w a s m a d e with the Z statistic,
E-mail: mribicich@fvet.uba.ar
Differences w e r e considered significant at p < 0.05.
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using the software Statistic for W i n d o w s .
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Parasite, 2001, 8, S246-S248
CONTROL AND VETERINARY DIAGNOSIS
RESULTS
DISCUSSION
B
oth animals in group 0 w e r e negative by artificial digestion. T h e predilection sites o f muscle
larvae o f Trichinella
spiralis
in pigs infected
with 100 larvae (group 1) w e r e in the b a s e o f the
tongue, the tongue, diaphragm, intercostals and the
shoulder; this muscle w a s the only representative o f
the commercial cuts w h e r e larvae were found. T h e five
most infected m u s c l e s in the others groups w e r e :
group 2: tongue, b a s e o f the tongue, diaphragm, left
fillet and b o s t o n butt. group 3: diaphragm, left masseter, tongue, b a s e o f the tongue, and boston butt and
group 4: diaphragm, tongue, left ham, boston butt and
b a s e o f the tongue. (Figs 1, 2 and 3 ) . Cranial muscles
to the last rib s h o w e d m o r e Trichinella
spiralis larvae
than those with a caudal location ( p < 0 . 0 1 ) . No significant differences w e r e found ( p > 0 . 0 5 ) b e t w e e n bilateral left and right muscles.
Parasite, 2001, 8, S246-S248
T
h e muscle groups in man that are most frequently the sites o f e n c y s t m e n t o f n e w b o r n
larvae are the extraocular muscles, the masseters, the muscles o f the tongue and larynx, the diaphragm, the m u s c l e s o f the n e c k , the intercostals
muscles and the deltoids. In addition, the portions o f
the muscle fibers nearest to the sites of attachment to
tendons and joints are most heavily infected (Campbell, 1 9 8 3 ) . T h e artificial digestion o f tissue samples
from 6 0 various muscles from 13 different sites of an
infected horse carcass s h o w e d that the muscles levator
labii maxillaris,
hyoideus
transversus
and
buccinator
w e r e the most heavily infected muscles. Muscles from
the tongue, the masseter and the diaphragm, which
have normally b e e n considered the muscles of c h o i c e
for meat inspection, w e r e the 4 , 6 and 1 3 most
infected muscles, respectively (Pozio et al., 1998). In
t h
Fig. 1. - Distribution of Trichinella
spiralis
larvae in muscle of pigs of group 2.
Fig. 2. - Distribution of Trichinella
spiralis
larvae in muscle of pigs of group 3.
X ICT. August 2000
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R I B I C I C H M . , M I G U E Z M., A R G I B A Y T . , B A S S O N . & F R A N C O A .
Fig. 3. — Distribution of Trichinella
spiralis
larvae in muscle of pigs of group 4.
experimentally infected pigs the tongue and diaphragm
w e r e t h e heaviest infected muscles f o l l o w e d b y the
muscles obliquus
abdominis
internus,
serratus
ventralis, psoas major, triceps brachi, biceps femoris,
semitendinosus,
intercostal,
semimembranosus
a n d longissimus muscle (Kotula et al, 1 9 8 4 ) .
In this work, fillet, h a m a n d shoulder w e r e t h e most
heavily infected followed b y other commercial cuts:
b o s t o n butt, spare ribs a n d belly. W e e m p h a s i z e that
Trichinella
spiralis w a s found in all the pigs inoculated
with m o r e than 5 0 0 larvae. In t h e case o f bilateral
muscles (masetters, intercostals, for e x a m p l e ) it is recom e n d e d to sample from both sides in order to avoid
falses negatives. It must b e noted that there w a s significant higher larvae concentration in the n e c k muscles
( b o s t o n butt), e v e n with l o w parasitic load; these
muscles are used to prepare cold meats. Commercial
cuts s h o w e d substantial w o r m burdens a n d in animals
infected with 5 0 0 to 5,000 Trichinella
spiralis
larvae
these muscles s h o w e d a parasitic load similar to the
s a m e muscles evaluated at t h e meat packing plant.
KOTULA A . W , MURRELL K . D . , ACOSTA-STEIN L. & LAMB L. Distri-
bution of Trichinella spiralis larvae in selected muscles and
organs of experimentally infected swine. Journal of Animal
Science, 1984, 58 ft), 94-98.
POZIO E, CELANO G . V . , SACCHI L., PAVIA C , ROSSI P., TAMBURINI A . , CORONA S. & LA ROSA G . Distribution of
Trichinella
spiralis larvae in muscles from a naturalle infected horse.
Veterinary Parasitology, 1998, 74, 19-27.
REINA D., MUNOZ-OJEDA M . C , SERRANO F . , MOLINA J . M . &
NAVARRETE I. Experimental trichinellosis in goats.
Parasitology, 1996, 62, 125-132.
Veterinary
STEWART G . L . & CHARNIGA L . M . Distribution of Trichinella
ralis in muscles of the mouse. Journal
1980, 66, 688-689.
of
spi-
Parasitology,
ZIMMERMANN W . J . Reproductive potential and muscle distribution of Trichinella spiralis in swine. Journal of American
Veterinary Medical.
Association, 1970, 156(6),
770-774.
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