Influence of muscular work and other factors on the course of the invasion of Trichinella spiralis

INFLUENCE OF MUSCULAR WORK AND OTHER FACTORS ON THE COURSE OF THE INV ASION OF TRICHINELLA SPIRALIS

BY

ZB[GNIEW KOZAR, MARIA KOZAR

Department of Parasitology, Polish Academy of Sciences, Warsaw

Among the various external factors acting upon the host and indirectly also on the parasite should be mentioned the activity of the muscles. One of the theories assumes even that the diaphragm and intracostal muscles are strongly invaded by T. spiralis because of their continuous work and active hyperaemia.

We bave decided to determine to what an extend this factor influences the in-

tensity of invasion (intestinal phase and muscular larvae) in the mouse. In the ex-

periments, as far as possible uniform mice were used, of the same age, males only,

of the a verage weight 14-17 g, kept on the same diet. The animals were infected

orally and received a strickly limited dose of 100 or 50 encysted larvae. To produce

tiredness the animals were kept for 4 hours daily in a specially constructed metal

drum, which revolved with a velocity of ca. 15 turns per minute .During this time

the animals were compelled to continuous active movement. Following a determined

period of time (10 or 40 days) all the mice of a given group were putto death and

the number of intestinal parasites or muscular larvae were counted. In the first

case the intestinal contents were accurately examined and the whole alimentary

tract was cut open, divided into sections and examined by the use of compressor

glasses. The sex of the parasites was also taken into consideration. In the case of

the muscular larvae (after 40 days) the weight of the diaphragm was previously

taken and the exact number of the parasites in the whole organ was counted. A sam-

3ti4

ple of 100 mg of muscles was also collected from the external side of the hind limb and the intensity of invasion, that is the exact number of the larvae was determined.

In the third series of experiments an additional group of mice (group 9) was selected and kept for several hours daily in a thermostat (37°C) and the group (8) of mice was submitted to slight generał ana~sthesia administered by daily sub- cutaneous injections of 0,00075 mg of luminal.

Every gro up numbered 10 mice. In spite of the fact that as far as possible the same technic of studies was used (equal infectious dose, accurate counting of the absolute number of parasites) there occurred in the separate groups fairly large deviations, which prove to be the result of some individual properties of every anima! and its influence on the invasion.

The first series included 2 groups of mice and every anima! was infected with 100 larvae to prove the eventual influence of muscular work on the course of the intestinal invasion. The mice of the first group were every day kept in the drum for 4 hours immediately following their --infection, the second group served as controls. All animals were put to death and examined on the 10th day following the infection.

The results are summarized in Table l:

Group

1

I

Period of physical work. Days folio- wing· infection

1-10 controls

:

Average number of intestinal trichinella on the 10th day fol- lowing infection

I

38,2

33,3 I

-·-~ --- · - - · -· ----··-···-

Number of parasi- Distribution of pa- tes according to sex rasites in intesti-

nes

- ----

66 I

^{small \ large}

11,9

j ^26,3 I ^37,8 I ^0,4

10,5 22,6 30,7 2,5

No striking differences were found between the two groups neither as regards the total number of parasites, nor in respect to the sexes. The sole difference is the rarer occurrence of the parasites in the large intestine in the experimental mice as compared with the controls. lt might be that physical work and the uervous stimuli accompanying to the every day treatment influenced the more rapid dis- charge of the parasites from the large intestine.

The results of experiments in respect to muscular larvae are shown in Table 2:

Taking into considerations the differences of the invasive

and the infectious doses, comparison can be made between the groups 3-6 and 7-10.

As shown in the Table 2, in the working mice between the 20-30 day following

infection (group 5) there were almost as many larvae found in the control animals

(group 6). A decline of the invasion was accentuated in comparison with the groups

3 and 6 - and was most significant in the group 4 that is in the group submitted

to physical work between the 10-20 day that is during the period of the most intensive

migration of the larvae. This proves that the daily work of muscles or other stimuli

STRESZCZENIA REFERATÓW

365

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accompanying the experiments significantly decrease the intensity of the invasion.

This was corroborated stili more clearly in the next series by comparing the group 7 (496 larvae) with the group 10, controls (1298 larvae). As shown in the next column of the Tabl(? 2, the same factors exerted an influence on the settlement of the larvae both in the muscles of the diaphragm and in the muscles of the limbs. It can be even said, that the differences were more significant in respect to the diaphragm.

1

; Average number Average number

of larvae in

I ^Series Period of physical ! Average number of of larvae in the i

work or other fac- , muscular larvae in ' d. h . , every mouse in

· ' iap ragm

every · muscles of limbs

!

tors. Days following : every mice in 200 mg : mice calculated per

I

^{i infection}

^{samples I} calculated per

2

¹⁰⁰ mg of muscles 100 mg of muscles

C, !

- ~ -

- - - -

work

3 1-10 531 354 192

work

11 4 , 10-20 395 244 119

work

5 20-30 653 426 353

I

6 controls 651 482 17. l

I I

,--:-ł

! I

work

i i

I 1 i 10-20 496 369 151

' _luminal

Ili 8 10-20 710 540 200

9 1 thermostat 37°C 590 483 145

10-20

10 i controls 1298 1065 353

Physical work is as a rule accompanied by active hyperaemia of the muscles and a decrease of the pH. Therefore theoretically a stronger muscular invasion could be rather expected. Similar to physical phenomena in muscles appear follow- ing the increased temperature. To a certain degree this is confirmed by our group 9, because all the mice were kept between the 10-20 day following infection for severa! hours daily in a thermostat (37°C). Comparing this group 9 with the groups 7 and 10 we are able to observe more or less the same effect as caused by physical work, that is a decrease of the invasion of over 50 per cent.

We expected to find a reverse phenomenon in mice remaining undisturbed

(group 8) during 10-20 days following infection. The mice were in a state of torpi-

dity caused by the daily injections of luminal. However, also in this group a decrease

of invasion took place as compared with the controls (IO) although the decrease

was not as marked as in the groups 7 and 9.

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Conclusions

1) By changing the living conditions of the host's organisrn it 1s possible to influence significantly the intensity of the parasitic invasions.

2) lt appears that the daily rnuscular work exerts no rnarked influence on the intestinal invasion by Trich. spiralis.

3) Significant differences, however, can be observed when tracing the rnuscular invasion and they depend on the period of applying the stimuli at various tirnes following the invasion.

4) Daily rnuscular work (and eventually other factors accompanying the treat- ment, nervous influences included) clearly decrease the intensity of rnuscular in- vasion, most strongly when applied between the 10-20 day follwing infection. The decrease of the degree of invasion is observed both in the diaphragmatic muscle and in other rnuscles (e. g. hind limb). This would indicate that continuous work and greater hyperaemia of the diaphragmatic muscle are not responsible for its normally stronger invasion.

5) A sirnilar phenornenon (decrease of invasion) was observed also after kee- ping the host's organism at 37°C.

6) Similarly, on the rnuscular invasion may exert influences factors of a

physiological nature, the essence of which can be established after further studies

are made on biochemical, hormonal, nervous and other factors. In view of the

fact that between the individuals of the same group considerable differences are

likely to appear it is essential to use always a greater number of experirnental animals

and controls.