Scientific journal
European Journal of Natural History
ISSN 2073-4972

IMMUNE STATUS OF HORSES AT CHRONIC STRONGYLOIDOSIS

Derkho M.A., Tkachenko A.V., Nurmukhametov N.V.
Strongyloidosis of horses refers to the class of helminthiases, which are caused by parasitizing intestinal worms Nematode of the superfamily Rhabditoidea, genus Strongyloides, species Strongyloidides westeri.

The disease´s agents parasitize in the small bowel, and though they are little pathogenic, under certain circumstances they can cause a nasty enteritis.

Strongyloidosis represents a unique genus: helmints are able both to parasitize in an animal´s body and to be free to propagate out of an organism. Only ambosexous females, which strike their eggs containing larvae by parthenogenesis (i.e. the development occurs from infertile egg cells), parasitize in the small bowel. After getting rid of the eggshells the larvae go through 4 phases developing into free-living males and females, and then helmints can propagate in the ambient medium.

The vermination can occur when ingesting - alimentarily, or through skin - percutaneously, free-living 3rd stage larvae, which then migrate through low tension circulation, lungs, breathing tube to the small bowel, where they develop into full-grown females.

Though there are lots of reasons for the helminthism to appear and they are all interconnected, one of the most important ones is the immune status change of animals, as it is stated that animals become more responsive to helminthisms at the immunity weakening (G.M. Urkkhart and co-authors, 2000).

That is why the aim of our work is to define the immune status of horses at chronic strongyloidosis on the basis of studying of the value of humoral immunity indexes in blood serum.

The research was carried out in the cavalry school "Squadron", Sovetsky, Khanty-Mansi Autonomous     Area,    Tumen    Region.  In  the experiment horses aged 3 years were used, two experimental groups being formed. The first group was the control one and consisted of clinically healthy animals. The second group was an experimental one, there were horses that were diagnosed to suffer from chronic srongyloidosis on the basis of clinical signs (parasitic enteritis) and the results of scatology by Fuelleborn-and-Berman-Orlov method, the occurrence of eggs and larvae of helmints in the fecal masses being proved.

The material of the research was fasting blood taken from the jugular vein in the morning and motionless. In the blood serum the value of immunoglobulins of A-, M-, and G-classes was defined by the single radial immune-diffusion method with the use of monospecific antiserums, the concentration of circulating immune complexes (CIC) - by the spectrophotometric method, blood serum lysozyme activity - on the selective lytic lysozyme activity concerning the sensitive culture Micrococus  lisodercticus, the bacterial growth-inhibitory activity - according the method of Smirnova O.V. (1996) were measured. The research results are shown in the table.

The host immunity limits the contamination level changing the development of new invasions or stopping their development completely or on larval phase, while the existing invasion with full-grown helmints either is extruded or their egg producing decreases considerably (G.M. Urkkhart and co-authors, 2000).

As it is seen from the tables 1 and 2, chronic invasion is accompanied with dyscrasia of humoral component of immune system. It is the after-effect of helmints´ allergenic influence on the host´s body and the interaction result of the system "antigen-antibody", helmints themselves and larvae migrants and their waste products playing the role of antigens.

Table 1. The immunoglobulin value in the horses´ blood serum, n=10 (Sx±x), * - Р ≤ 0,001

Animal

groups

Immunoglobulin classes, g/l

Ig G

Ig M

Ig A

Control

16,51±0,53

2,29±0,11

1,86±0,06

Experimental

22,30±0,65*

2,39±0,13

1,03±0,10*

The analysis of the results of the study of immunoglobulin value in blood serum of the horses at chronic invasion showed that the quantity of IgG increases by 34-37%.

70-80% of the total immunoglobulin value in blood serum is allotted on IgG. They play the main and foundational role in humoral immunity at antigenic loading causing the pathogenic agent´s death with a compliment factor and opsoning the phagocytal cells; are able to neutralize bacterial exotoxins, to bind compliment and to react precipitation.

IgG increasing testifies the adaptive humoral immune reaction of a body to the helminthism invasion and is connected with the influence of nematodes´ antigens, their waste products, their self-tissue and the following-up bacterial population destruction. The IgG level increase may also be associated with the fact that the mucus membrane with hyperpermeability allows anthelmintic immunoglobulin G to "go out" of plasma into bowel lumen and to have an access to parasites.

We haven´t established authentic IgМ level change at chronic horse strongyloidosis. It is known that immunoglobulins of the class M are "the earliest" of all immunoglobulin classes. They are able to agglutinate bacteria, neutralize viruses, activate compliment.

The data got by us testify a greater probability that IgМ-antibodies don´t participate in chronic invasion pathogenesis.

We have established that chronic srongyloidosis of horses is accompanied with an authentic decrease of the IgА level by 40-45%.

Immunoglobulin A is a secretory immunoglobulin. It refers to the main immunoglobulin class which is concerned with local immunity, prevents bacteria from attaching to the mucus membrane, neutralizes enterotoxins, activates phagocytosis and compliment. The IgA concentration decrease allows assuming the existence of suppressive mechanisms at chronic invasion, which can underlie the synthesis inhibition of immunoglobulins of the given class.

Besides, it has been established that in the acute period of nematodosis of gastrointestinal tract at heavy beasts and sheep the adaptive immunity to helminthisms is formed. The immune response is a complex one, and is based on the antigenic stimulation with secretory or excretory products egested during the development of a 3rd stage larva into a full-grown species. For example, the experimental research showed that mature sheep possessing the immunity to Ostertagia can ingest up to 50000 3rd stage larvae daily without any clinical signs of parasitic gastritis. There are also the data that the secretion of anthelmintic immunoglobulin A on the mucus membrane surface promotes the functional blennogenous cell´s activity increase.

Therefore, the IgА concentration breakdown promotes (at reinvasion of horses with nematodes´ larvae) larvae´s migration, their development into full-grown species, their fertility increase and, as the consequence, helmints´ disease-evoking power´s increase. It leads to the fact that helminthism occurs with pronounced clinical signs.

We have established that the horse body responds to the entry of nonshared antigens with the synthesis of proteins possessing specific affinity to the antigen which causes this synthesis. This conditions the appearing in the blood circulating immune complexes (CIC), the concentration of which is one of the criteria of functional competence of the humoral component of the immune system of animals (Isayev A.G., 2001). The CIC level at chronic invasion increases more than by 30%, that can be the consequence of non-sufficient rate of utilization by the elimination of the given complexes against the background of the increased antigenic loading to a body.

Table 2. The humoral immunity indexes, n=10 (Sx±x), * - Р ≤ 0,05; ** - Р ≤ 0,01

Indexes

Control group

Experimental group

Circulating immune complexes, %

25,85±0,66

31,15±1,63*

Blood serum bactericidal activity, %

66,88±2,47

80,09±2,57**

Blood serum lysozyme activity, %

27,37±1,23

34,50+0,84**

One of humoral resistance factors is the lysozyme enzyme, the place of synthesis of which macrophages , from where it enters blood and then leucocytes (granulocytes), serve. The biological meaning of lysozyme is founded on its antibacterial properties. In our research we have established the authentic increase of lysozyme and bactericidal blood serum activity, that testifies the state tension of natural defensive mechanisms of horses and their and agent interplay level, i.e. the stimulation of the phagocytosis process during chronic invasion.

So, we have established that the immune status of horses at chronic strongyloidosis is characterized by IgG level increase and IgA concentration decrease. The specific redistribution of main immunoglobulin classes in blood serum of animals, probably, creates favorable conditions for larvae´s migration in the host body after the vermination, the development of the 3rd stage larvae into a full-grown species, nobilous female fertility increase and their disease evoking power increase. That is why chronic invasion occurs with pronounced clinical signs in the image of parasitic enteritis. Alongside with local disorders conditioned by helmints parasitizing in animals´ bowels the CIC concentration, bactericidal and lysozyme activity increase occur. It means that nobilous helmints, larvae migrants, their waste products and secretory and excretory products egested during the development of a 3rd stage larva into a full-grown species appear as antigenic stimulator for a horse body.

The data got allow us to make the conclusion that helminthic invasion is not a separately taken pathology, but represents a difficult system complex appearing as the result of host body affect with helmints and is accompanied with animals´ immune status changes. That is why it is necessary to include the preparations decreasing the sensibilizing action of helminthic invasion on the host body and increasing the synthesis of immunoglobulin of class A into helminthism treatment schemes additionally alongside with anthelmintic agents.

The article is admitted to the International Scientific Conference «Problems of national educational standards´ international integration», France, Great Britain, 2007, April 20-27; came to the editorial office on 16.11.06