Genetic evidence substantiates transmission of Trichinella spiralis from one swine farm to another

BACKGROUND

Trichinella spiralis ranks seventh in the risk posed by foodborne parasites. It causes most human cases of trichinellosis and is the most frequent cause of Trichinella outbreaks on pig farms and in wild boar, worldwide. Veterinary inspectors seek the source of outbreaks in hopes of limiting the spread. Established molecular tools are inadequate for distinguishing among potential T. spiralis infection sources because genetic variability in these zoonotic pathogens is limited in Europe. Microsatellite markers proved successful in tracing an outbreak of T. britovi, a related parasite harboring much more genetic variation. Here, we successfully employed microsatellite markers to determine the genetic structure of T. spiralis isolates from two pig outbreaks, discovering notable uniformity among parasites within each farm and discovering an epidemiological link between these two outbreaks.

METHODS

The individual larvae from five isolates of T. spiralis from two pig farms and from ten wild boars were genotyped using nine microsatellite markers to examine their genetic structure.

RESULTS

Notably uniform parasite populations constituted each farm outbreak, and the parasites from the first and second outbreaks resembled each other to a notable degree, indicating an epidemiological link between them. Wild boar harbored more genetically variable larval cohorts, distinguishing them from parasites isolated from domestic pigs.

CONCLUSIONS

Microsatellite markers succeeded in distinguishing isolates of the highly homogeneous T. spiralis, aiding efforts to track transmission. Each outbreak was composed of a homogenous group of parasites, suggesting a point source of contamination.

Epidemiology and hypothetical transmission cycles of Trichinella infections in the Greater Kruger National Park of South Africa: an example of host-parasite interactions in an environment with minimal human interactions

Knowledge on the epidemiology, host range and transmission of Trichinella spp. infections in different ecological zones in southern Africa including areas of wildlife-human interface is limited. The majority of reports on Trichinella infections in sub-Saharan Africa were from wildlife resident in protected areas. Elucidation of the epidemiology of the infections and the prediction of hosts involved in the sylvatic cycles within specific ecological niches is critical. Of recent, there have been reports of Trichinella infections in several wildlife species within the Greater Kruger National Park (GKNP) of South Africa, which has prompted the revision and update of published hypothetical transmission cycles including the hypothetical options based previously on the biology and feeding behaviour of wildlife hosts confined to the GKNP. Using data gathered from surveillance studies and reports spanning the period 1964-2019, confirmed transmission cycles and revised hypothesized transmission cycles of three known Trichinella species (T. zimbabwensis, Trichinella T8 and T. nelsoni) are presented. These were formulated based on the epidemiological factors, feeding habits of hosts and prevalence data gathered from the GKNP. We presume that the formulated sylvatic cycles may be extrapolated to similar national parks and wildlife protected areas in sub-Saharan Africa where the same host and parasite species are known to occur. The anecdotal nature of some of the presented data confirms the need for more intense epidemiological surveillance in national parks and wildlife protected areas in the rest of sub-Saharan Africa to unravel the epidemiology of Trichinella infections in these unique and diverse protected landscapes.

Outbreak of Trichinella T9 Infections Associated with Consumption of Bear Meat, Japan

An outbreak of trichinellosis occurred in Japan in December 2016. All case-patients had eaten undercooked bear meat, from which Trichinella larvae were subsequently isolated. DNA sequencing analysis of the mitochondrial genes cytochrome c-oxidase subunit 1 and internal transcribed spacer 2 confirmed that Trichinella T9 had caused the outbreak.

[Trichinellosis outbreaks in Aragón (1998-2017)]

OBJECTIVE

In Aragon, official veterinary controls to detect the presence of Trichinella in meat products have allowed trichinosis to be a low-incidence disease in the form of outbreaks associated with family consumption of meat products that are not sanitarily controlled. The aim of the work was to describe the epidemiological characteristics of the trichinosis outbreaks that occurred in Aragon during the study period and the action measures carried out, which served as a basis for redesigning and strengthening prevention and control measures.

METHODS

Descriptive study of the characteristics of time, place, person, food implicated, etiological agent and control measures implemented in the outbreaks identified by the Epidemiological Surveillance Network of Aragón from 01/01/1998 to 31/12/2017. For the descriptive analysis, the mean with its standard deviation and proportions were calculated.

RESULTS

During the study period (from 01/01/1998 until 31/12/2017) there were 7 family outbreaks with 294 exposed, 103 cases (Attack Rate 35%), of which 29 were hospitalized (28.1%). The case fatality rate was 1%. The average age of the cases was 43.3 years (standard deviation 15.9). 70.8% of the cases were male. Outbreaks were concentrated between December and May. Five outbreaks originated after consumption of wild boar. The etiological agent identified in meat and/or biological samples from the cases was Trichinella spiralis in four outbreaks and Trichinella britovi in two other outbreaks, while the agent could not be identified in one outbreak. In all outbreaks, actions were carried out in accordance with the recommendations established by the National Epidemiological Surveillance Network (RENAVE).

CONCLUSIONS

Trichinosis in Aragon takes the form of sporadic family outbreaks coinciding with the time of wild boar hunting and home slaughtering of pigs and is associated with the consumption of meat products not controlled sanitarily, so it is necessary to strengthen health education and intersectoral collaboration in the development and implementation of prevention and control strategies.

Occurrence of Trichinella spp. in rats on pig farms

INTRODUCTION

The highest risk of trichinellosis for human is considered in eating meat products containing live larvae, mostly from wild boars or pigs. Spreading of Trichinella spp. may occur in various ways, one of which is transmission by vectors. The rat is considered to be the most common vector for Trichinella parasite. The population of rats living on pig farms can play an important role in maintaining or spreading the parasite to other animals.

OBJECTIVE

The aim of presented survey was to investigate the occurrence of Trichinella spp. in rats on farms with pigs infected with this parasite.

MATERIAL AND METHODS

From pig farms selected for study, the muscles of collected rats were investigated by magnetic stirrer digestion method to assess occurrence of Trichinella in the rat population. Isolated Trichinella parasites were identified under stereomicroscope and multiplex PCR were performed for species identification.

RESULTS

Rats infected with Trichinella spp. were discovered on three of five investigated pig farms. The mean extent of invasion in rats from the studied farms was 23.33%. The calculated medium intensity of invasion was 4.09 lpg (larvae per gram) (SD 5.41). All larvae of Trichinella discovered from rats were identified as T.spiralis.

CONCLUSIONS

The results obtained indicate that in farms with a high prevalence of Trichinella invasion in pigs there are very likely to be found rats infected by this nematode. This suggests possibility to maintain the invasion in herd and spread into neighborhood farms.

The dynamics of Trichinella spiralis epidemiology: Out to pasture?

The great public health success in prevention of human trichinellosis has resulted in a decades-long decline in the incidence and health impact of this zoonosis. The important elements of this achievement include improvement in animal husbandry practices, meat inspection, consumer education, and medical care. Most outbreaks now involve consumption of infected game. However, domestic pork still accounts for many outbreaks, mostly in Eastern Europe and Argentina, where traditional small, "backyard" rearing of pigs for household and local use often involve high risk rearing practices, especially the feeding of food waste. Although commercially produced pork under controlled management now accounts for about half of the world's pork production the demand by consumers, especially in Europe and North America, for free-range pork is increasing. Because of the varying degrees of outdoor exposure in free-range systems, there is concern that such exposure increases the risk of spillover of Trichinella spiralis, (also Trichinella britovi and Trichinella pseudospiralis in Europe) from wild animal reservoirs. This review examines the knowledge gaps hindering the risk assessments needed to provide the producers with guidelines for achieving the food safety assurance demanded by consumers.

[Trichinae, pigs and veterinary public health: The introduction of the microscopic world into the scientific basis for meat inspection (Barcelona, 1870s)]

During the second half of the 19th century, Spanish authorities began developing specific programs on the safety of certain foods intended for human consumption. This paper analyses the key features that gave rise to the inclusion of the veterinarian in the administrative structure responsible for safeguarding public health. Among the aspects covered, special focus is put on the relationship between human and animal medicine at a time when growing public alarm in relation to certain zoonoses contributed to shaping the notion of veterinary public health. The appearance of a disease in pigs that was transmissible through the consumption of parasitized meat set the scene for veterinary inspection to be associated with the protection of public health. The outbreaks of trichinosis all over Spain in the 1870's proved the existence of contagium animatum in a pre-bacteriology era, and this led to the introduction of improvements in food inspection. In this sense, microscopic examination of pork products encouraged the modernization of inspection tasks undertaken by veterinarians, which had previously focused on the organoleptic evaluation of meat and fish and on unveiling fraud. The introduction of microscopes was widely accepted and established a watershed between acceptable and unacceptable methods of carrying out the examination of meat. Furthermore, this "technological" method of diagnosis brought veterinary medicine closer to other more prestigious health professions, at least in theory. Among other aspects, the acceptance of trichinae as an exogenous cause of disease contributed to 19th century doctors learning about the idea of pathogenic microorganisms from veterinarians. At a social level, the use of the microscope was seen as a way of preventing the transmission to people of an animal disease that was very much in the public eye at the time. From the political point of view, the process -analysed in this paper from the perspective of veterinarians in Barcelona- allows a glimpse of the contrast between the desire of some Catalan veterinarians to modernize their profession and what was happening in others parts of Spain.

[ROLE OF ANIMALS AND HUMAN BEINGS IN THE SPREAD OF TRICHINOSIS IN THE KURSK REGION]

Trichinosis is natural focal invasion in the Kursk Region. Porkworms (Trichinella) circulate in natural biocenoses among wild carnivorous mammals, wild boars, and rodents. Trichinosis cases are recorded in synanthropic animals. Carnivorous mammals form the basis for the parasitic system of trichinosis. The animals are infected with Trichinella through carnivorism, necrophagy, and cannibalism. The transport Trichinella vectors, necrophagous insects, naturally play an insignificant role-in the spread of trichinosis. Trichinella infection in animals occurs more commonly through necrophagia and cannibaism during winter months. Not only animals, but also man, play a great role in the spread of trichinosis. Infested wild and synanthropic aninals inhabiting the Kursk Region may carry the risk for Trichinella infection in the population.

[Possible sources of Trichinella infection in the indigenous population of Chukotka]

Statistical methods confirmed that the dietary intake of traditionally made meat from marine mammals and polar bear could cause Trichinella infection in the residents of the communities of the Chukotka Peninsula.

[Gastropods and their role in the transmission of Trichinella invasion]

Gastropods were established to be able to absorb decapsulated and encapsulated Trichinella larvae located in muscle tissue. Trichinella larvae remain viable and infectious for 24 to 48 hours after passing through the gastrointenstinal tract of gastropods.

[Parasitological monitoring as part of epidemiological surveillance of helminthiasis in the Russian Federation]

The paper presents data on the prevalence of helminthiasis in Russia on the basis of the State Reports on the sanitary and epidemiological situation in the Russian Federation. It comparatively characterizes morbidity rates in 2010-2012. Morbidity analysis has revealed the main reasons for the prevalence of parasitic diseases and the possible ways of their elimination.

Trichinella infections in animals and humans in sub-Saharan Africa: a review

The aim of this review is to provide information on Trichinella infection in humans, livestock and wildlife in sub-Saharan Africa mainly focusing on geographical distribution of species/genotypes, biology, host range, life cycles and to identify research gaps. Trichinella britovi, Trichinella nelsoni and Trichinella zimbabwensis and one genotype (Trichinella T8) are known to occur in sub-Saharan Africa. Distinct geographic ranges with overlapping of some taxa in some areas have been observed. Genetic variants of T. nelsoni has been reported to occur among parasites originating from Eastern and Southern Africa and sequence heterogeneity also occurs among T. zimbabwensis isolates originating from different regions of Zimbabwe and South Africa. Field observations so far indicate that sylvatic Trichinella infections in the region are common in carnivores (mammals and reptiles) and to a lesser extent in omnivores. Cannibalism, scavenging and predation appear to be the most important routes of transmission and maintenance of the sylvatic cycles of the Trichinella taxa. To date, human trichinellosis has been documented in only four sub-Saharan countries (8.7%, 4/46). Bushpigs and warthogs have been the source of human infection with T. britovi and T. nelsoni being the aetiological agents. An increase in bushmeat trade and the creation of Transfrontier Conservation Areas (TFCAs) may have increased the risk of human trichinellosis in the region. With the creation of TFCAs in the region, sampling of wildlife hosts from protected areas of most sub-Sahara African countries is required to fully map the distribution of Trichinella species/genotypes in this region. More structured field surveys are still needed to determine the sylvatic host distribution of the different Trichinella taxa. Biological data of the Trichinella taxa in both wild and domestic animals of sub-Saharan Africa is very limited and further research is required.

[Monitoring of animal trichinellosis in the Czech Republic--the past and present]

The nematode Trichinella spp. is the etiological agent of trichinellosis, a zoonotic parasitic disease. Many carnivorous and omnivorous animal species may become infected with Trichinella spp., including humans. Trichinella spp. is transmitted orally through consumption of raw or undercooked meat. There is a general agreement that animals do not get sick following infection. However, the course of infection in humans includes disease that can range from subclinical to fatal. Because of its role in human disease, there are increasing global requirements for reliable diagnostic and control methods for Trichinella in food animals to ensure meat safety. This review article describes the biology and history of human and animal trichinellosis in the Czech Republic, and recommended test methods as well as modified and optimized procedures that are used in meat inspection programmes.

[Significance of birds in the dissemination of Trichinella spp. larvae in coastal and aquatic biocenoses]

The real possibilities of mechanical transmission of trichinae through avian feces to terrestrial and aquatic mammals with the participation of a number of invertebrates (ostraceans, crustaceans, and dipteran larvae) and fishes were studied. Laboratory models have proven that the mammals can be biologically infected with trichinosis from the above species of vertebrates and invertebrates, the mechanical vectors of this infestation.

Trichinellosis surveillance - United States, 2002-2007

PROBLEM/CONDITION

Trichinellosis is a parasitic disease caused by roundworms of the Trichinella genus. Humans are incidental hosts who become infected after ingestion of raw or undercooked meat containing encysted larvae of Trichinella spp. Common signs and symptoms of trichinellosis include eosinophilia, abdominal pain, fever, periorbital edema, and myalgia. National surveillance has documented a decline in the reported incidence of trichinellosis in the United States since 1947, the first year nationwide data were collected systematically. The decreased incidence of trichinellosis has mirrored the decrease of Trichinella in commercial pork products as a result of changes in pork industry management standards and government regulations. In addition, an overall decrease has occurred in the number of cases of trichinellosis related to pork consumption. During 1997-2001, meats other than pork were the most common source of infection, and more cases were associated with home-raised pork than with store-bought pork.

REPORTING PERIOD COVERED

2002-2007.

DESCRIPTION OF SYSTEM

Trichinellosis is a reportable disease in 48 states and has been a nationally notifiable disease since 1966. Cases are defined by clinical characteristics and the results of laboratory testing for evidence of Trichinella infection. States report cases to CDC through the National Notifiable Diseases Surveillance System. Reported cases are summarized weekly and yearly in MMWR. In addition, states are asked to submit a standardized case report form with supplementary case data to CDC's Division of Parasitic Diseases.

RESULTS

During 2002-2007, a total of 66 cases of trichinellosis were reported to CDC. Those cases for which a supplementary case report form was not submitted or that did not meet the case definition were excluded from analysis. Of the 66 cases reported during 2002-2007, a total of 12 (18%) cases were excluded from analysis. Associated meat products were classified as either pork or meat products other than pork and were identified for 43 (80%) cases. Meat products other than pork were associated with 27 (50%) cases: 21 with bear meat, one with either bear or deer meat, one with cougar meat, one with deer meat, one with walrus or seal meat, and two with commercial beef. Pork was associated with 10 (19%) cases: seven with commercial pork, two with noncommercial pork, and one with an unspecified type of pork. Of the seven cases associated with consumption of commercial pork, five were linked to U.S. commercial pork, and two were attributed to pork ingested during travel in Asia. The two cases associated with noncommercial pork were attributed to wild boar meat; one case involved wild boar meat from a farm and the other wild boar meat from a farmers' market. Six patients reported consuming both pork and meat products other than pork, but the infected meat product could not be identified.

INTERPRETATION

The number of reported trichinellosis cases attributed to commercial pork consumption remains low. The greatest number of cases continues to be associated with consumption of meat other than pork, especially bear meat.

PUBLIC HEALTH ACTION

For the incidence of trichinellosis in the United States to be reduced further, education regarding safe food preparation practices and prevention of trichinellosis should be targeted toward hunters and other consumers of wild game meat, especially bear.

Trichinellosis outbreak in Bavaria caused by cured sausage from Romania, January 2007

In mid-January 2007, three family members from Bavaria came down with typical symptoms for trichinellosis after visiting relatives in Romania (Arad district) during the Christmas holidays.

A case of trichinellosis in Denmark, imported from Poland, June 2007

A 59-year-old Danish woman presented to her general practitioner (GP) at the end of June. A few weeks earlier, during a meal at home in Denmark, she had consumed a slice of pork sausage (‘teewurst’, German sausage) brought to her by three Polish visitors.

[Methods for investigating Trichinella infections in domestic and wild animals]

Trichinellosis is an important parasitic zoonosis that is caused by the intracellular nematode Trichinella spp.. Infection of humans occurs through consumption of raw (or undercooked) meat containing infectious larvae. In Europe, meat from pork, horse, and wild boar have been identified as most important sources of Trichinella infections in humans. In Switzerland, both the domestic pig and wild boar population are considered free of Trichinella. Conversely, Swiss foxes, lynxs and recently a wolf were found to be infected, the species identified in these animals was always referred to as Trichinella britovi. Although this species rarely infects pork and, compared to Trichinella spiralis, only causes reduced pathogenic effects in humans, the basic presence of Trichinella in Switzerland cannot be neglegted. This fact has gained increasing importance since the responsible authorities in the European Union (EU) are preparing regulations for the official Trichinella-control in meat in order to improve food safety for consumers. These regulations will be implemented as a consequence of the recent association of east European countries with the EU. This new legislation particularly takes into account, that in the past by far most cases of human trichinellosis in the EU were due to consumption of imported east European meat.Within the framework of the bilateral agreements of Switzerland with the EU, the Swiss veterinary public health authorities will have to comply with the foreseen EU regulations. Although diagnostic methods for the direct demonstation of Trichinella in pork meat are already routine practice in several Swiss abattoirs, the implementation of a meat control program for Trichinella for the entire slaughter pig population of the country would lead to an enormous increase in costs for the administration and will require an increased infrastructure in veterinary services. In order to find a reduced testing format for monitoring Trichinella infections in Swiss pork, an infection risk-oriented survey strategy is currently evaluated. In the present article, this minimized survey strategy is discussed regarding its compatibility with the EU regulations laying down rules for the official control of meat for Trichinella.

Trichinella zimbabwensis in wild reptiles of Zimbabwe and Mozambique and farmed reptiles of Ethiopia

In 1995, a new species of Trichinella (Trichinella zimbabwensis) was discovered in farmed Nile crocodiles (Crocodylus niloticus) in Zimbabwe, where the mode of transmission was the consumption of the meat of slaughtered crocodiles, used as feed. To determine whether T. zimbabwensis affects poikilotherm vertebrates in the wild, monitor lizards (Varanus niloticus) and Nile crocodiles were collected in Zimbabwe and Mozambique. In 5 (17.6%) of the 28 monitor lizards from Zimbabwe, T. zimbabwensis larvae were identified. For the wild Nile crocodiles from Mozambique, species-level identification was not possible, yet immunohistochemical analysis revealed that 8 (20%) of the 40 animals harboured non-encapsulated Trichinella sp. larvae, which probably belonged to T. zimbabwensis. This is the first report of T. zimbabwensis in wild reptiles, and the findings are consistent with reports that vertebrates with scavenger and cannibalistic behaviour are the most important hosts of Trichinella spp. The wide distribution of monitor lizards and crocodiles in Africa and the development of national crocodile breeding programs in many African countries should be taken into consideration when evaluating the risk of transmission of this parasite to mammals, including humans.

Human outbreak of trichinellosis in the Mediterranean island of Sardinia, Italy

Trichinella sp. infection has been documented in both humans and animals in most Mediterranean countries, yet in the past 60 years no infections have been reported on the Mediterranean islands. We describe the first outbreak of Trichinella sp. infection to have been reported on the island of Sardinia. The outbreak occurred in two villages in 2005 and involved 11 persons who had eaten raw sausages made from the same free-ranging sow. All 11 persons developed signs and symptoms of trichinellosis and seroconverted within 48 days of consuming the infected meat. The etiological agent was Trichinella britovi. Sardinia, like all Mediterranean islands, had been considered to be Trichinella-free. The present report, together with a recent report of T. britovi infection in animals on the nearby island of Corsica (France), raises questions as to the validity of the concept of Trichinella-free areas or regions.

Human infections due to nematode helminths nowadays: epidemiology and diagnostic tools

An update on the epidemiology of intestinal and tissue roundworms, in the world as well as in Italy, is presented. This analysis indicates that the most important changes happened in developed countries, where two main phenomena have been registered. The improvements occurred in social, economic, hygienic and sanitary conditions resulted in decrease of intestinal geohelminth prevalence but, besides, the changes happened at level of other factors, like environment, climate and human behaviour, promote more and more the opportunity for infections due to animal nematode species, which in people induce tissue syndromes. Therefore, the easier circulation of zoonoses among humans constitutes the main remark, which has to be strongly taken into account in countries like Italy, in that it is an emerging sanitary problem, important both for the number of people involved, and for the difficulties induced by their diagnosis. The general trend of "traditional" and "new" nematode infections that can affect humans is analysed, changes in the distribution patterns are tentatively explained, and available diagnostic tools are summarised.

Cluster of trichinellosis cases in Mecklenburg-Vorpommern, Germany

Seventeen cases of trichinellosis were detected among members of an extended family living in the state of Mecklenburg-Vorpommern, eastern Germany

Recent advances on the taxonomy, systematics and epidemiology of Trichinella

Since Owen first described Trichinella as a human pathogen in 1835, the number of organisms comprising this genus has grown dramatically. Where it was once thought to be a monospecific group, this genus is now comprised of eight species and three additional genotypic variants that have yet to be taxonomically defined. Along with the growth in the genus and description of the parasites has come a concomitant increase in our understanding of the epidemiology and geographical distribution of these organisms. Recent expansion of the non-encapsulated group to include three species biologically defined by their unique host ranges encompassing mammals, birds and reptiles, has raised substantial questions as to the term, 'Trichinella-free' as it applies to geographical localities. A true appreciation of the adaptability of this genus to host and environmental selection factors, as well as its dissemination to the far reaches of the world can best be appreciated by reviewing what we know and what we hope to know about this ancient and elusive parasite. The review herein consolidates our current understanding of the taxonomy, epidemiology, and phylogeny of the genus Trichinella, and identifies areas where data are lacking and our knowledge requires additional clarification.

The epidemiology of human trichinellosis in China during 2000-2003

The endemic foci of trichinellosis continue to be mainly located in the southwestern, the central and northeastern China. The seroepidemiological surveys of T. spiralis infection in humans were carried out in six Provinces or Municipals (P/M) of China during 2000-2003, the overall seroprevalence was 3.57%. From 2000 to 2003, 17 outbreaks of human trichinellosis, with 828 cases and 11 deaths, were recorded in 8 P/A of China. All of 11 deaths occurred in the southwestern China (1 case in Sichuan, 4 cases in Tibet and 6 cases in Yunnan), where the ethnic groups have the habit of eating raw meat. Pork is the predominant source of outbreaks of human trichinellosis in China. Out of 17 outbreaks, 13 (76.47%) outbreaks were caused by eating raw or poorly cooked pork, 2 (11.77%) outbreaks caused by eating raw dog meat and 2 (11.77%) outbreaks by eating game meat (wild boar and bear), suggesting the increasing significance of dog and game meat as source of infection for human trichinellosis. The partial effects of health education interventions for control of trichinellosis have been achieved in some counties of Yunnan province. The number of inhabitants eating raw meat has decreased from 72.74% (1561/2146) before interventions to 47.43% (489/1031) after interventions. The decrease of incidence of trichinellosis in China during the past 4 years was probably due to a combination of factors, including the reduction in the prevalence of Trichinella infection in domestic swine, the strengthened meat inspection, the increased use of home freezers and the development of heath education practice.

[Epidemiology of human trichinellosis in Poland--currently and in the past]

Since the XIX century human trichinellosis has remained an unsolved problem of public healthcare in Poland. This paper describes the past situation and analyses current changes in the epidemiological pattern of trichinellosis in Poland. Epidemiological data from the last 60 years, point out that the number of human cases as well as the number of deaths caused by trichinellosis has decreased significantly. Up to 90s the main source of Trichinella infection for people was pork. Among other implemented control measures, the introduction of the artificial digestion method in the early 80s to detect trichinellosis in pigs resulted in a shift in the sources of Trichinella infection in humans - pork was replaced with wild boar meat. In the years 1990-1995 the number of outbreaks due to pork consumption was 3.5-times higher than in the years 2000-2005. In the early nineties pork was the source of infection causing about 71% of all outbreaks; in 2000-2005 that number has fallen to only 12%. On the other hand wild boar meat was responsible for 23% of the outbreaks in 1990-1995 and as many as 88% of all outbreaks in the years 2000-2005. Moreover the number of persons infected in the outbreaks significantly decreased. The study of wild animals demonstrated that wild boars in Poland are infected not only with T. spiralis but also with Trichinella britovi. These results and EU recommendations indicate a requirement of determining the Trichinella species which cause infections in outbreaks. In the 3 trichinellosis outbreaks in 2005 the infected meat products were examined with molecular tools. T. spiralis species larvae were the etiological agents of infection in all these outbreaks. The current epidemiological situation of trichinellosis in Poland indicates a need of increasing the awareness of risks related to wild boar meat consumption among the general public. Introducing the artificial digestion method as an obligatory method for wild boar meat examination is also necessary.

[Wild and domestic animals as permanent Trichinella reservoir in Poland]

BACKGROUND

[corrected] Since Owen first described Trichinella as a human patogen in 1835, the number of organisms comprising this genus has grown dramatically. This etiological agent of human trichinellosis shows worldwide distribution in domestic and/or sylvatic animals.

MATERIAL AND METHOD

The aim of the presented paper was to determine the distribution of Trichinella species in wild animals such as red foxes, wolves, wild boars, and domestic pigs in Poland. Muscle samples from diaphragm and forelegs were collected from animals killed by hunters. Muscle larvae were recovered from the muscle after artificial digestion and identified at the species level by RAPD, PCR-RPLF and multiplex PCR.

RESULTS

Of 75 nematode isolates from red foxes: (Vulpes vulpes), 50 resulted as T. britovi, 6 T. spiralis, 6 were mixed infections of these two species. Fifteen Trichinella isolates remained unidentified. Of 97 nematode isolates from wild boars (Sus scrofa), 21 resulted as T. britovi, 69 T. spiralis, 2 were mixed infections of these two species. Five Trichinella isolates remained unidentified. Of 6 examined wolves (Canis lupus) killed in the Bieszczady region, 3 animals were positive against T. britovi. Of 6 examined raccon dogs (Nyctereutes procyonoides) from Pomorskie region, 2 animals were positive against T. spiralis. Of 21 nematode isolates from domestic pigs, 1 resulted as T. britovi and 21 as T. spiralis. Up to date, two Trichinella species are detected as the etiological agents of epidemiology among domestic and wildlife animal in Poland: T. britovi is the dominant species in red foxes and T. spiralis is the dominant species in wild boars and domestic pigs.

Red fox (Vulpes vulpes) cannibalistic behaviour and the prevalence of Trichinella britovi in NW Italian Alps

Food habits of the red fox (Vulpes vulpes) were studied in the Aosta Valley region (NW Italian Alps) and were related to the prevalence of Trichinella infection in the red fox itself and in two Mustelid species (the stone marten (Martes foina) and the badger (Meles meles)). The search of Trichinella by the automatic digestion of muscles samples led us to determine a prevalence of 3.5+/-1.2% in red foxes, 7.9+/-4.3% in stone martens and 1.9+/-1.8% in badgers, with no significant differences among the species. All larvae were identified as Trichinella britovi. The fox diet was assessed through the analysis of both faeces (n=180) and the stomach contents of road-killed animals (n=109). Our results confirmed the opportunistic feeding behaviour of the red fox, which is able to use various trophic resources, both of animal and vegetal origin: e.g. wild and cultivated fruits (F%=47.1; V%=67.3), rodents (F%=22.8; V%=64.8) and carrion (F%=15.6; V%=78.6) formed the bulk of the fox's diet. The frequency of occurrence of potential events of cannibalism was 1.0%, even if the complete absence of undigested remains, other than hairs, suggested the possibility of confusing cannibalism with coat-cleaning. We suggest that intra-specific necrophagy could not represent the unique way of transmission of the nematode in natural conditions.

Congenital trichinellosis in experimentally infected mice

The present study aimed at allocating the time during pregnancy at which transplacental transmission of Trichinella spiralis (T. spiralis) larvae took place. Swiss albino mice were infected at different durations of pregnancy; five days before mating, on gestation day zero and five days after mating. Furthermore, to study the effect of immunosuppression on transplacental transmission, half of the experimental mice were immunosuppressed using cyclophosphamide drug (Endoxan). The percentage of infected uteri, embryos and placentas and the mean larval count were calculated on day 8 post infection (PI). Moreover, the percentage of infected offspring and the mean larval count in their muscles were estimated on day 30 PI. The results of the present study revealed that, transplacental transmission of T. spiralis could occur in offspring of mice when their mothers are infected before or after pregnancy. This was documented by the presence of larvae in the muscles of offspring. However, the rate of this transmission increased when the mothers are infected at late pregnancy whether they were immunosuppressed or not. The administration of the immunosuppressive drug whether before or after pregnancy increased the rate of infection and the mean larval count in both uteri of mothers and muscles of their offspring. A higher percentage of abortion was demonstrated in females infected before mating in different studied groups.

Studies on vertical transmission of Trichinella spp. in experimentally infected ferrets (Mustela putorius furo), foxes (Vulpes vulpes), pigs, guinea pigs and mice

Vertical transmission of Trichinella spiralis was evaluated in ferrets (n=21), foxes (n=11), pigs (n=12), guinea pigs (n=16), and mice (n=41). The placental barrier to be crossed by migratory Trichinella larvae varies structurally in different animal species. Ferrets and foxes have an endotheliochorial placenta structure, guinea pigs and mice a haemochorial, and pigs an epitheliochorial placenta. The non-encapsulating Trichinella pseudospiralis larvae have an extended muscle migration prior to entering a muscle cell. To evaluate if T. pseudospiralis was more likely to be transmitted to offspring, an additional group of foxes (n=11) infected with T. pseudospiralis was included. Two different dose levels were used for ferrets, pigs, guinea pigs, and mice. In pigs and guinea pigs, infection was given at different times of the gestation period. Vertical transmission, measured as recovery of muscle larvae in the offspring, was demonstrated in both ferrets groups, in all four guinea pig groups, and in the high dose mouse group, but not in any fox or pig groups.

[Preliminary study on congenital transmission of Trichinella spiralis in mice]

OBJECTIVE

To study congenital transmission of Trichinella spiralis in mice and observe the protection of anti-Trichinella antibodies from the infected dams to challenge infection.

METHODS

According to the gestation (fertilization), the Kunming mice were divided into two groups: the infected group after gestation and the gestated group after infection. New-born mice were cut into small pieces to separate the larvae within 1 day after birth. One-day-old offspring born to normal dams were nursed by the infected dams, slaughtered after 21 days and examined for the larvae. Serum anti-Trichinella antibody level in offspring born to the infected dams was assayed by ELISA at different time after birth, and its immune protection against challenge infection was studied.

RESULTS

Out of 6 offspring born to the dams infected at 7 days after fertilization, two were found to be infected. Among other female mice which were first infected with T. spiralis and then gestated, only the offspring born to the dams fertilized at 8 and 22 days after infection were found to be infected, the infection rate of offspring was 20% (2/10) and 25%(2/8) respectively. All larvae recovered from the young were non-encapsulated. The cross-fostering experiment showed that none of 30 offspring born to normal dams were found to be infected. The serum antibody positive rate in 27 offspring born to the infected dams at 1,7,24, and 40 days after birth was 100%, 100%, 77.8% and 14.8%, respectively. The worm reduction rate in the offspring 40 days after birth was 62.0% after challenge infection. The worm reduction rate in mice in which sera from the offspring born to the infected dams were passively transferred was 55.7%, there was a significant difference (P<0.01) compared to the control group.

CONCLUSION

A transplacental transmission of T. spiralis is revealed in mice. Anti-Trichinella antibodies from the infected dams may partially protect the young from challenge infection.

First record of human trichinosis in Chile associated with consumption of wild boar (Sus scrofa)

The first South American case of human trichinosis, resulting from the consumption of roast wild boar (Sus scrofa) is reported in Chile. The patient presented fever, diarrhea, myalgias, facial edema, sub-conjunctival reddening, photophobia, eosinophilia, and elevated glutamic oxalacetic transaminase. The diagnosis was confirmed by two immunoenzymatic tests (ELISA) using somatic and excretion-secretion antigens.

Serosurvey of selected zoonotic agents in polar bears ( Ursus maritimus )

Between 1982 and 1999 blood samples were collected from 500 polar bears (Ursus maritimus) captured in the Beaufort and Chukchi seas, to determine the seroprevalence of Brucella species, Toxoplasma gondii, and Trichinella species infections. The bears were classified into four age groups, cubs, yearlings, subadults and adults. Brucella and Toxoplasma antibodies were detected by agglutination (a buffered acidified card antigen and rapid automated presumptive test for brucellosis and a commercial latex agglutination test for toxoplasmosis); an ELISA was used to detect Trichinella antibodies. The overall seroprevalence of Brucella species was 5 per cent, and subadults and yearlings were 2-62 times (95 per cent confidence interval 1.02 to 6.82) more likely to be seropositive for Brucella species than adults and their cubs. The antibody prevalence for Toxoplasma gondii was 6 per cent, and for Trichinella species 55.6 per cent. The prevalence of antibodies to Trichinella species increased with age (P<0.001).

Inappropriate feeding practice favors the transmission of Trichinella papuae from wild pigs to saltwater crocodiles in Papua New Guinea

The recent discovery of Trichinella zimbabwensis in farmed crocodiles (Crocodilus niloticus) of Zimbabwe and its ability to infect mammals, and the development of both T. zimbabwensis and Trichinella papuae in experimentally infected reptiles led to an investigation of Trichinella infection in saltwater crocodiles (Crocodylus porosus) and in wild pigs (Sus scrofa) of Papua New Guinea, to see if T. papuae also, is present in both cold- and warm-blooded animals. Of 222 crocodiles examined, 47 animals (21.2%), all from Kikori, Gulf Province, were positive for non-encapsulated larvae in the muscles. The greatest number of larvae was found usually in the biceps, with an average of 7 larvae/g. One isolate from a crocodile infected successfully both laboratory rats and mice. Of 81 wild pigs examined, 9 from Bensbach river area (Western Province) and 1 from Kikori area (Gulf Province) were positive for non-encapsulated larvae in the muscles. Trichinella larvae from both saltwater crocodiles and wild pigs have been identified by multiplex-PCR analysis as T. papuae. The sequence analysis of the region within the large subunit ribosomal DNA, known as the expansion segment V, has shown the presence of a molecular marker distinguishing T. papuae isolates of Bensbach river area from those of Kikori area. This marker could be useful to trace back the geographical origin of the infected animal. The epidemiological investigation carried out in the Kikori area has shown that local people catch young crocodiles in the wild and keep them in holding pens for several months, before sending them to the crocodile farm in Lae (Morobe Province). They feed the crocodiles primarily with wild pig meat bought at the local market and also with fish. These results stress the importance of using artificial digestion for routinely screening of swine and crocodiles, and of adopting measures for preventing the spread of infection, such as the proper disposal of carcasses and the adequate freezing of meat.

The epidemiological investigation of Trichinella infection in brown rats (Rattus norvegicus) and domestic pigs in Croatia suggests that rats are not a reservoir at the farm level

Whether the brown rat (Rattus norvegicus) is a reservoir of Trichinella spp. infection or merely an accidental host, which may be vector of Trichinella spp., continues to be debated. We estimated the prevalence of Trichinella sp. infection in brown rat populations and in domestic pigs in 2 villages in Croatia, where Trichinella sp. infection in pigs has been endemic in the past 10 yr. Trichinella spiralis larvae, identified by a multiplex polymerase chain reaction analyses, were the only species detected in both rats and pigs. In 2001 and 2002, 2,287 rats were collected on 60 farms with different levels of sanitation and with, or without, T. spiralis-infected pigs. The prevalence of infection in rats ranged from 0.2 to 10.7%. Infected rats were detected only on farms with T. spiralis-positive pigs and low sanitation or formerly with low sanitation (P = 0.007, Fisher's exact test), yet no infected rat was detected on farms with T. spiralis-negative pigs. The finding that no infected rat was found on farms with T. spiralis-negative pigs suggests that, in the investigated area, the brown rat is not a reservoir but only a victim of improper pig slaughtering.

Experimental Trichinella infection in seals

The susceptibility of seals to infection with Trichinella nativa and the cold tolerant characteristics of muscle larvae in seal meat were evaluated. Two grey seals, Halichoerus grypus, were inoculated with 5000 (100 larvae/kg) T. nativa larvae and two grey seals with 50000 (1000 larvae/kg). One seal from each dose group and two control seals were killed at 5 and 10 weeks post-inoculation (p.i.). At 5 weeks p.i., infection was established in both low and high dose seals with mean larval densities of 68 and 472 larvae per gram (lpg), respectively, using eight different muscles for analyses. At 10 weeks p.i., mean larval densities were 531 and 2649 lpg, respectively, suggesting an extended persistence of intestinal worms. In seals with high larval density infections, the distribution of larvae in various muscles was uniform, but in one seal with a low larval density infection, predilection sites of larvae included muscle groups with a relative high blood flow, i.e. diaphragm, intercostal and rear flipper muscles. Trichinella-specific antibody levels, as measured by ELISA, increased during the 10 week experimental period. Infected seal muscle was stored at 5, -5 and -18 degrees C for 1, 4 and 8 weeks. Muscle larvae released from stored seal muscle by artificial digestion were inoculated into mice to assess viability and infectivity. Larvae from seal muscle 10 weeks p.i. tolerated -18 degrees C for 8 weeks but larvae from seal muscle 5 weeks p.i. tolerated only 1 week at -18 degrees C, supporting the hypothesis that freeze tolerance increases with the age of the host-parasite tissue complex. The expressed susceptibility to infection, extended production of larvae, antibody response and freeze tolerance of T. nativa in seals are new findings from the first experimental Trichinella infection in any marine mammal and suggest that pinnipeds (phocids, otariiids or walrus) may acquire Trichinella infection by scavenging even small amounts of infected tissue left by hunters or predators.

Infectivity of Trichinella nativa in traditional northern (country) foods prepared with meat from experimentally infected seals

The infectivity of Trichinella nativa larvae in three traditional northern (country) foods was assessed. Foods were prepared with meat from seals experimentally infected with Trichinella nativa and evaluated over a 317-day period during which this food was fed directly to cats while mice were orally inoculated with larvae recovered following the digestion of the food in a solution containing 1% pepsin and 1% HCl at 37 degrees C. Foods examined were igunaq (meat and blubber placed in a seal skin bag and allowed to ferment), nikku (air-dried meat), and sausage (meat, fillers, salt, and spices). Sausage was examined both in a raw state and after partial cooking. Infective T. nativa larvae survived in igunaq, nikku, raw frozen sausage, and poorly cooked sausage for at least 5 months under controlled laboratory conditions. Core temperatures of partially cooked sausage never exceeded 50 degrees C. Caution should be exercised in using these data to establish guidelines for the consumption of raw products, since the survival of infective larvae could be unpredictably extended under field conditions. These data indicate significant food safety risks associated with igunaq, nikku, and sausage prepared with Trichinella-infected meat and provide information for use in risk management and in directing future research.

TOLERANCE TO LOW TEMPERATURES OF DOMESTIC AND SYLVATIC TRICHINELLA SPP. IN RAT MUSCLE TISSUE

The present study was designed to investigate the tolerance to low temperatures of 9 Trichinella isolates in rat muscle tissue. Nine groups of 24 rats were infected with encapsulated Trichinella spiralis, Trichinella nativa, Trichinella britovi, Trichinella murrelli, Trichinella T6, Trichinella nelsoni, and 3 nonencapsulated Trichinella pseudospiralis strains. Six rats from each of the groups were necropsied at 5, 10, 20, and 40 wk postinfection (wpi). Muscle tissues containing Trichinella larvae were exposed to temperatures of -18, -5, and 5 C for 1 or 4 wk, and afterward the reproductive capacity index (RCI) in mice was determined for the 9 individual Trichinella isolates. Only T. nativa muscle larvae were infective after freezing at a temperature of -18 C. At 5 wpi all encapsulated isolates, except for the tropical species T. nelsoni, remained infective after exposure to a temperature of -5 C for both 1 and 4 wk, whereas nonencapsulated T. pseudospiralis survived only 1 wk of exposure. All Trichinella spp. remained infective after exposure to a temperature of 5 C. Muscle larvae for all investigated species remained infective as long as they persisted in live rats during the experiment. Analysis of variance showed a significant effect of age on the temperature tolerance of encapsulated T. spiralis and nonencapsulated T. pseudospiralis. In addition, significant interaction between age of muscle larvae and length of exposure was found. In general Trichinella muscle larvae of medium age (10 and 20 wpi) tolerated freezing better than early and late stages of infection (5 and 40 wpi). This is the first study to demonstrate such a relationship between age of infection and temperature tolerance of Trichinella spp. muscle larvae.

Trichinellosis: old facts and new developments

Trichinellosis is a helminth zoonosis, which is known since long, but which is emerging or re-emerging in several regions of the world. During the last years the number of cases of trichinellosis in pigs and man in several East-European countries has increased very much due to the breakdown of the veterinary services because of the difficult political and socio-economic situation. In several third world countries on the other hand trichinellosis has become more important due to the increasing number of small traditional pig farms, in which the hygienic conditions are suboptimal. Furthermore, outbreaks of human trichinellosis have been reported due to recently discovered new species such as T. pseudospiralis and T. papuae. Over the last 25 years horsemeat has been more important as a source of human trichinellosis within the European Union than pork or wild boar meat. In Belgium, however, no cases of human trichinellosis have been reported since 1979. A review is presented of the available data on animal trichinellosis in Belgium. The potential risk for the consumer is discussed. Finally, some suggestions are made for a new approach of trichinellosis control in Belgium and the European Union.

Trichinellosis in China: epidemiology and control

The first outbreak of human trichinellosis in China, according to official national publication, was registered in Tibet in 1964. Since then, more than 500 outbreaks, numbering 25161 cases with 240 deaths, have been recorded. However, this reported quantity is probably highly underestimated because adequate diagnostic techniques might not have been available in the whole area. Moreover, infection in animals is widespread over China, with the prevalence of pig trichinellosis being as high as 4% in some provinces. The estimated situation of trichinellosis in China highlights the necessity not only for its control, but also for the government to elaborate new regulations and guidelines for animal inspection.