Trichinellosis

High prevalence of T. spiralis infection with the vast range of animal hosts was revealed in the 1960s in the Russian Arctic from the Archangelsk region to Chukotka. The circulation of infection is considered to be supported by a high viability of parasite larvae in carcasses of wild animals (carnivores food) in winter. Also, by the migration of polar bears and polar foxes from North Atlantic in the west to the Bering sea in the east. Thalarctos maritimus can cover a distance up to 80km and more in 24h. It was believed that marine animals were involved in the transmission of Trichinella through carnivorous birds excrement contaminated by parasite larvae and washed into a sea or through bottom Crustacea consumed by seals. Six outbreaks of trichinellosis in man involving 97 cases were recorded from the late 1950s to the end of the 1960s in northern Europe and Asiatic part of the USSR (Shikhobalova et al. 1969). In 1957, a severe outbreak of trichinellosis involving more than 40 persons with one lethal case occurred in the north of the Leningrad region. The source of infection was undercooked and salted pork, also pigs had been fed by the carcasses of caged silver foxes (Ozeretskovskaya et al. 1958). The scheme of Trichinella circulation in the animals of the Arctic was suggested (Ozeretskovskaya and Uspensky 1957).

The clinical features and the course of disease from the bear Trichinella strain on the Bennet Island (Th. maritimus) and from KPAD (Ursus arctos) were characterized by a long incubation period (30-35 days). The disease is manifested by hypertermia, skin rashes, general oedema, delirium, hallucinations, and in some cases by acute abdominal pains with haemorrhage syndrome and a hypereosinophilia. The latter in the patient from the Bennet Island outbreak reached 88% (24816 cells per millilitre) (Ozeretskovskaya and Uspensky 1957; Ozeretskovskaya 1968). The peculiarity of clinical features of trichinellosis from the northern strains of Trichinella (T. spiralis var. nativa today) is due to its poor compatibility with a human and a mice host that manifesting by a protracted intestinal development of the parasite, a violent cell infiltrations around the larvae in muscle tissue and the destruction of larvae, as a muscle biopsy of patients showed (Ozeretskovskaya 1968; Ozeretskovskaya and Pereverzeva 1976). The experimental study of Trichinella strain from Th. maritimus by Franz Josef Land revealed a stable low invasiveness for mice, the peculiarities of proteins content (disc electrophoresis in polyacrilamid gele) as compared with the laboratory (primarily synanthropic swine) strain in mice from the Martsinovsky Institute, a rather poor ability of the larvae incapsulation in mice muscle tissue; a higher sensitivity to thiabendazole. In contrast to the two-layered fibrous-hyaline capsules of larvae in animals from temperate areas capsules of arctic trichinella larva in polar bears and polar foxes have irregular form, multi-layered, with unequal hyaline regeneration of encapsulated portion of the sarcoplasm (Ozeretskovskaya and Pereverzeva 1976). The study of 146 isolates of Trichinella from wild animals of various regions of Eurasia by cross-breeding methods revealed T. spiralis var. nativa

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in Arctic islands and in Galarctic zone of Russia (Shaikenov 1995). One presumes that there is a sympatric spread of T. spiralis and T. pseudospiralis in the nature and in synanthropic foci in Russia with infected birds as a link (Garkavi and Zverzhanovsky 1999). The high sera reactivity of patients with trichinellosis myocarditis and cardiomyodystrophia to a-myosin cardiac peptide (known to induce experimental allergic myocarditis, Wegmann et al. 1994) revealed recently (Ozeretskovskaya et al. 2000) corresponded with the clinical and morphological pattern of allergic myocarditis developed in guinea pigs sensitized with somatic Trichinella antigens with lanoline and mineral oil (without BCG) (Ozeretskovskaya 1976).

The incidence of trichinellosis in the previously endemic foci of Ukraina, Belorussia, and the Central Europe regions of Russia was almost zero in the 1970s. The new economic development of the Russian North and the Northeast in the 1970s caused the mass influx of population from the regions of the country free of zoonotic helminthic infections. The incidence of trichinellosis in Russia became 16-fold higher during 1971-1975 and the source of infection in 96% of patients was bear or wild boar meat. The outbreaks were registered in the Magadan region, Kamchatka and Sakhalin Island, the Krasnoyarsk, and the Khabarovsk regions. Out of 377 cases of trichinellosis registered in Russia in 1976-1977, 178 (47.2%) belonged to the outbreaks in the North and the Northeast of the country. Bear meat accounted for 96.6% of these 178 cases. In the industrial region of Taimir peninsula 132 (62.3%) cases of trichinellosis were registered in 1984-1993, with 80 (37.7%) of them in rural areas. Ursus arctos meat accounted for 84 (39.6%) cases, pork accounted for the other 60.4% (Knjazev 1994). More than 200 cases of trichinellosis caused by bear meat were registered in the Sakhalin and in Kamchatka in 1978. Trichinellosis caused by bear meat was up to 43% in 1979 and only about 30% in 1980. The decline of the portion of trichinellosis caused by bear meat was in some way the result of reviving of endemic trichinellosis in the Europe regions of Russia (Ozeretskovskaya 1979). The incidence of trichinellosis in Russia was about 700-1000 cases per year in 1990-1994. Forty-three outbreaks of infection with 594 cases including 54 from the bear and a wild boar meat were registered in 1995. Forty-three outbreaks with 789 cases of infection but with only 13 of them from bear meat were notified in 1996. In total, 1383 cases (two lethal ones) of trichinellosis were registered in 1995-1997 in Russia, with pork accounting for 80% of them. Outbreaks connected with infested bear meat occurred in Krasnoyarsk region and in Kamchatka (Ozeretskovskaya 1997a). In 1998, the infection was contracted only in two cases through bear meat in the Krasnoyarsk region and in five cases through dog meat in the Irkutsk region and Kamchatka. In 2000, only 483 cases of trichinellosis were registered in Russia, 105 (21.9%) them in the Northeast part of the country, particularly in the Krasnoyarsk, Irkutsk, and Khabarovsk regions (81, or 16.8% cases). The general decline of the incidence of the infection is due to the strict sanitary-veterinary checking of meat.

Sero-epidemiological study (indirect ELISA technique) including 713 persons (519 children) in the northern regions of Russia (the Federal Programme 'Children of the North', see above) in 1995-1996 revealed the highest seroprevalence of trichinellosis in HMAD and the lowest one in Chukotka: 11.1 and 1.5-5, respectively. The rather high percentage of diagnostically significant titres in HMAD might be connected with the ethnically mixed group examined. Only children were examined in Chukotka (Table 6.1). In KPAD, seroprevalence was 5, but in 2.2 of the examined cases, the titres were of diagnostic significance (Table 6.1). In aboriginals of the Tomsk region and in the Taimir peninsula seroprevalence of trichinellosis was equal. However, diagnostic titres in the former were higher than that of epidemiological significance (11.1 and 7.1, respectively) and was the highest among the diagnostic titres in all surveyed regions (Table 6.1). In none of examined regions, outbreaks of trichinellosis was

Table 6.1 Seroprevalencea of helminthic infections of medical-social significance in the North of Russia

Region

No. of

No. of adults Group of

Infections

children

examined population

E.

E.

T. T.

canis

examined

granulosus

multilocularis

spiralis

KPAD

131

49Mixed

2.1b

0c

5 (2.2)d

15.4

(7.7)

Tomsk

5

94Aboriginals

6.4 (9.6)

12.8 (3.2)

7.1

14.1

(111)

(42.4)

Taimir

51

Aboriginals

(2)

(3.9)

7.8 (2)

5

peninsula

HMAD

201

51Mixed

5.9 (1.5)

3.9

11.1

14.2

(6.3)

(115)

Chukotka

131

Aboriginals

15

1.5-5

4.6

(mostly)

Notes

a Epidemiologically significant titres, %. b In children; in adults 6.1. c In children; in adults 2.2.

d In brackets here and further - diagnostically significant titres.

registered during the survey. One presumes that in the Tomsk region some cases of trichinellosis might be diagnosed as acute opisthorchiasis. The lack of clinically manifesting trichinellosis in the indigenous population of the North of Russia in spite of a high seroprevalence of the infection even in children (see HMAD in Table 6.1), seems to be the result of an early and permanent infestation or of some kind of tolerance to parasite antigens (see section on 'Opisthorchiasis').

Clinically manifesting cases of trichinellosis in Russia are treated with albendazole at 5-10mg per kg for 5-10 days. Glucocorticides are administered in the severe, complicated cases only for 3-7 days, simultaneously with albendazole. For moderately severe cases a combination of the latter with adenylate-cyclase cAMP-proteinkinase inhibitors (voltaren, brufen) and the replacement of glucocorticides by this combination in the severe cases as soon as possible are recommended. The preventive treatment with benzimidazole carbamates of persons who have consumed infected meat is widely used (Ozeretskovskaya and Sergiev 1994; Ozeretskovskaya et al. 1994).

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