Trichinella (Eger, 2011)

Akimov, I. A., Didyk Trichinellosis, Yu. M., It, Trichinella, Trichinella, Gamble, Up, Trichinella, Based, Trichinella, T., T, T., T, T., T, T., T, T., T, T., T, T., T, T, Trichinella, T, T, The, T., T, T., T, T., T, Pozio, Murrell, Sharma, The & Trichinella, 2020, Trichinellosis Of Wild Animals In Ukraine And Its Danger To The Public, Zoodiversity 54 (5), pp. 411-418 : 413-416

Trichinella prevalence in Ukraine

The important source of Trichinella sp. infection for humans in Ukraine remains pork and game. According to the State Research Institute for Laboratory Diagnostic, Veterinary and Sanitary Examination, more than 1000 domestic pigs infected with Trichinella larvae were identified over the past 20 years (Reports of the CVL of Ukraine, 1986 –2018). According to the official data of the Sanitary and Epidemiological Station of Ukraine, more than 1500 people were infected with trichinellosis over the past 30 years in Ukraine (Reports of the CSE of Ukraine, 1986 –2018). According to our research in 2002–2018, Trichinella spp. found in all regions of Ukraine ( Akimov, Didyk, 2018). Trichinella was detected in 3 % of wild boars, 15.5 % of wolves, 16 % of foxes, 12 % of martens, 10 % of badgers and 20 % of raccoon dogs ( Didyk, Akimov, 2016; Akimov, Didyk, 2018). The prevalence of Trichinella infection in wild boars is 3 %, and in predators — 16 % ( Didyk, Akimov, 2016). For carnivores, the infection intensity ranges from 50 to 300 larvae per gram of muscle tissue ( Didyk, Akimov, 2016). These rates are very high. We’ve identified a growing tendency of infection prevalence for carnivores, over the last 30 years in Ukraine: from 3.5 % in I. A. Kondratyev’s studies of 1972–1976 and 8.8 % in N. A. Kulikova’s works of 1986 –1987, up to 15 % nowadays ( fig. 3 ) ( Akimov, Didyk, 2017).

Using modern molecular genetic methods, we demonstrate the presence of three species of the genus Trichinella in Ukraine: T. spiralis , T. britovi and T. nativa ( Akimov et al., 2005; Akimov, Didyk, 2016). In the sylvatic cycle, T. britovi was found in 96 % of the infected animals, T. nativa in 3 % and T. spiralis in 1 % of wild animals. Our results were confirmed by the International Commission on Trichinellosis (ICT, Italy), adding it to the Trichinella global database ( T. spiralis ISS1594 ; T. britovi: ISS1590, 1591 , 1592, 1593; T. nativa ISS1595 ). T. britovi is the dominant species in the sylvatic cycle in Ukraine ( fig. 4 ). It was found in all species of wild animals (wild boar, lynx, wolf, fox, marten, raccoon dog and badger).

For the first time, the expansion of T. nativa was observed. Among all Trichinella species found in Ukraine, this one is the most aggressive against humans. T. nativa was detected in Chernihiv, Poltava, Sumy and Kherson Regions in wolves and foxes. T. spiralis was found in wild boars in Zhytomyr and Mykolaiv Regions. The cases of mixed infections T. britovi – T. spiralis were found in carnivores in Kherson Region ( Akimov, Didyk, 2016; Didyk, Akimov, 2016).

All Trichinella species detected in Ukraine are extremely pathogenic to humans.

The incidence of trichinellosis in Ukraine

There is almost no information about the incidence of human trichinellosis in Ukraine in the current publications ( Derbal, 1997; Shelemba, 1999). A. S. Bessonov, the famous researcher of Trichinella and trichinellosis, described Ukraine in the early XX century as an area of a stationary synanthropic outbreak of trichinellosis, with the annual mass infestations among domestic swine and mass outbreaks of trichinellosis among the local population ( Bessonov, 1970). Vinnytsia, Odesa and Khmelnytskyi Regions were the most dangerous for trichinellosis of pigs. Up to 70 % of animals infected with trichinellosis were annually recorded in these particular areas, as well as the majority of human cases ( Bessonov, 1972). From 1946 to 1972, Ukraine ranked second in the incidence of trichinellosis among the population of the ex-Soviet countries. From 40 to 146 cases of human infection were registered annually, the highest number of cases (500–700 patients annually) was recorded in Belarus ( Bessonov, 1972; Pavlov, 1972).

The situation changed in the mid-1990s, when the special “Instruction on the diagnosis, prevention and elimination of trichinellosis of animals (No. 23 of May 23, 1995)” was accepted by veterinary medicine experts. Mandatory and strict rules of the disease diagnosis were established in order to prevent infection of humans and animals.

According to the Center for Disease Control and Monitoring of the Ministry of Health of Ukraine, more than 1500 cases of human trichinellosis were recorded in 1986–2018, with the mortality rate of 0.5 %. The figures are very high. The incidence rate of the local population in Ukraine is compared to the “critical one” in Southeast Asia and Africa ( Pozio, 2007; Rostami et al., 2017). The largest synanthropic outbreak of trichinellosis related to the consumption of pork meat took place in the Dnipropetrovsk Region (40 % of all cases in the country) in the late XX early XXI century. The level of infection is also high in Mykolaiv, Kyiv, Donetsk, Khmelnytsky and Kharkiv Regions of Ukraine ( fig. 5 ).

The cases of trichinellosis related to the consumption of infected game were record- ed in the Zakarpattia, Odesa, Volyn, Zhytomyr and Kyiv Regions (Reports of the CSE of Ukraine, 1986 –2018) .

Small but persistent outbreaks of trichinellosis were recorded in Lviv, Ivano-Frankivsk, Chernivtsi, Chernihiv, Cherkasy and Kherson Regions, as well as isolated cases of human infection.

In the European Union, the trichinellosis test of domestic and wild animals and the implementation of measures to prevent infection are given priority. In 2017, 15 EU/EEA countries reported 224 cases of trichinellosis, of which 168 were confirmed and 56 were probable. The overall notification rate was 0.03 cases per 100,000 population. Bulgaria, Croatia and Romania accounted for 73.8 % of confirmed cases. The highest notification rate reported in Bulgaria (0.77 cases per 100,000 population), followed by Croatia (0.51), Lithuania (0.32) and Romania (0.24) (Trichinellosis — Annual Epidemiological Report. 2017). It was found that in 72 % of cases, the human infection was caused by T. spiralis and in 28 % by T. britovi . Reporting data on the incidence of trichinellosis is mandatory in all European countries it is included in compulsory annual monitoring of zoonoses and zoonotic agents ( Directive 2003 /99/EC List A). The cases are widely announced and all the necessary measures are taken to prevent the spread of the infection.

Prevention of risk for human trichinellosis

Products derived from pig and wild boar meat remain the most important sources of human trichinellosis. Consuming undercooked meat from pigs or hunted wild animals which have not been tested for Trichinella is a main risk factor for trichinellosis in Ukraine. It is vital that relevant information reaches consumers of meat products. According to legislation of Ukraine, it is mandatory for all animals (pig, horse and wild animals) which are potential source of Trichinella spp. parasites and are intended for human consumption to be examined for Trichinella larvae with one of several approved methods (Instruction on the prevention and control of trichinellosis in animals). The artificial digestion technique is the standard, sensitive, efficient, and cost effective method used to detect Trichinella larvae in meat ( Rostami et al., 2017; Noeckler et al., 2019).

To help prevent Trichinella infection in animal populations, farmers or hunters do not allow pigs or wild animals to eat raw meat, scraps, or carcasses of any animals which may be infected with Trichinella larvae.

There are several ways to prevent trichinellosis: cook the meat to a safe temperatures or freeze small pieces of pork for 20 days at –15 °C to kill any worms. Freezing wild game meats, unlike freezing pork products, may not effectively kill all worms because some worm species that infect wild game ( T. nativa ) are freeze-resistant.

Salting, drying, smoking, or microwaving meat alone does not consistently kill infective Trichinella worms; homemade jerky and sausage were the cause of many cases of trichinellosis reported in Europe and Ukraine in recent years.

According to official data there were about 50,000 of wild boars and about 10,000 were hunted in 2011, so, 300 animals, or 3 %, could be infected with Trichinella ( Eger, 2011) . Stay away from meat or meat products from domestic and wild animals that have not been tested for Trichinella .

Figures

Fig. 3. The infestation extent of wild mammals’ trichinellosis in Ukraine.

Fig. 4. T. britovi occurrence in natural foci of invasion in Ukraine.

Fig. 5. Frequency of trichinellosis for the population of Ukraine, 1986–2018.