Risk-based surveillance for meat-borne parasites.

There is a plethora of meat-borne hazards - including parasites - for which there may be a need for surveillance. However, veterinary services worldwide need to decide how to use their scarce resources and prioritise among the perceived hazards. Moreover, to remain competitive, food business operators - irrespective of whether they are farmers or abattoir operators - are preoccupied with maintaining a profit and minimizing costs. Still, customers and trade partners expect that meat products placed on the market are safe to consume and should not bear any risks of causing disease. Risk-based surveillance systems may offer a solution to this challenge by applying risk analysis principles; first to set priorities, and secondly to allocate resources effectively and efficiently. The latter is done through a focus on the cost-effectiveness ratio in sampling and prioritisation. Risk-based surveillance was originally introduced into veterinary public health in 2006. Since then, experience has been gathered, and the methodology has been further developed. Guidelines and tools have been developed, which can be used to set up appropriate surveillance programmes. In this paper, the basic principles are described, and by use of a surveillance design tool called SURVTOOLS (https://survtools.org/), examples are given covering three meat-borne parasites for which risk-based surveillance is 1) either in place in the European Union (EU) (Trichinella spp.), 2) to be officially implemented in December 2019 (Taenia saginata) or 3) only carried out by one abattoir company in the EU as there is no official EU requirement (Toxoplasma gondii). Moreover, advantages, requirements and limitations of risk-based surveillance for meat-borne parasites are discussed.

Early diagnosis of experimental Trichinella spiralis infection by nano-based enzyme-linked immunosorbent assay (nano-based ELISA).

Trichinellosis is a serious foodborne zoonotic disease. It is an important threat to public health all over the world. Although anti-Trichinella IgG detection is the most widely used method for diagnosis of trichinellosis, but there is an obvious window between clinical symptoms and positive serology. Gold nanoparticles (AuNPs) can be conjugated with antibodies affording them promising applications for bio-chemical detection. Herein, AuNPs-based ELISA was evaluated for the first time in the detection of Trichinella spiralis circulating antigen (CAg) for its potential as a diagnostic tool of experimental infection. Swiss Albino mice were orally inoculated with 100 muscle larvae/mouse. Animals were sacrificed 6, 8, 10, 12, 14, 16, 22 and 28 day-post infection (dpi). Blood samples were tested for CAg by both standard ELISA and nano-based ELISA using anti-rabbit polyclonal IgG conjugated with AuNPs. CAg was only detected by nano-based ELISA 6, 8, 10 dpi and by both formats 12-28 dpi. Nano-based assay recorded a statistically significant high sensitivity (58.33%, 91.67%) and accuracy (72.22%, 94.44%) 8 and 10 dpi, respectively in comparison to standard ELISA. Both assays showed high sensitivity and accuracy 12-28 dpi. Thus, nano-based ELISA could be considered as an early sensitive diagnostic method for experimental trichinellosis.

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.

Meat sources of infection for outbreaks of human trichinellosis.

Trichinellosis is one of the most important foodborne zoonotic diseases, with worldwide distribution. While human risk for trichinellosis has historically been linked to pork, modern pork production systems and slaughter inspection programs have reduced or eliminated pork as a source for trichinellosis in many countries. While pork may no longer pose a significant risk for trichinellosis, many other animal species may be hosts for Trichinella species nematodes and when human consume meat from these animal species, there may be risk for acquiring trichinellosis. This review article describes the various non-pork meat sources of human trichinellosis outbreaks, where these outbreaks have occurred and some of the factors that contribute to human risk. The literature reviewed here provides evidence of the persistence of Trichinella as a human health risk for people who eat meat from feral and wild carnivores and scavengers, as well as some herbivores that have been shown to harbor Trichinella larvae. It points to the importance of education of hunters and consumers of these meats and meat products.

Studies on vertical transmission of Trichinella spiralis in experimentally infected guinea pigs (Cavia porcellus).

An experimental study to enhance knowledge on the capability of Trichenella spiralis to pass from guinea pigs to progeny at different periods of pregnancy or lactation was performed. For this purpose, 18 female adult guinea pigs were inoculated with 100 or 1000 T. spiralis muscle larvae (ML) during early, late gestation and during lactation period. The presence of T. spiralis (ML) in mothers and newborns was studied through enzymatic digestion from muscle samples. ML were observed in 9 of 42 newborn guinea pigs and levels of infection were significantly higher when infections of mothers were done during late gestation (p = 0.0046) with the high infective dose (p = 0.0043). T. spiralis ML were not recovered from any of the newborns from mothers infected in the lactation period. Ten out of 18 infected mothers presented larvae 1 in their mammary glands. Muscle samples from the tongue and the masseter showed the highest larval burdens. These observations confirm previous reports on that ML of T. spiralis are capable to pass through placental tissues to reach and encyst in striated muscle groups of newborn guinea pigs. This study may also reinforce the importance of preventive programs to control trichinellosis in those endemic areas where pregnant women would have high risk of infection.

Trichinella and polar bears: a limited risk for humans.

In this review, we identified 63 cases reported since World War II of human trichinellosis linked to the consumption of parasitized polar bear (Ursus maritimus) meat. This low number contrasts to the numerous cases of human trichinellosis related to consumption of the meat of black (U. americanus) or brown bears (U. arctos). The prevalence of Trichinella infection is high in bears, but larval muscular burden is usually lower in polar bears compared to other bear species. Polar bears, therefore, seem to play a limited role in the transmission of trichinellosis to humans, as native residents living in the Arctic traditionally consume well-cooked bear meat, and travellers and foreign hunters have only limited access to this protected species due to the declining polar bear population.

Outbreak of trichinellosis related to eating imported wild boar meat, Belgium, 2014.

Trichinellosis is a rare parasitic zoonosis caused by Trichinella following ingestion of raw or undercooked meat containing Trichinella larvae. In the past five years, there has been a sharp decrease in human trichinellosis incidence rates in the European Union due to better practices in rearing domestic animals and control measures in slaughterhouses. In November 2014, a large outbreak of trichinellosis occurred in Belgium, related to the consumption of imported wild boar meat. After a swift local public health response, 16 cases were identified and diagnosed with trichinellosis. Of the 16 cases, six were female. The diagnosis was confirmed by serology or the presence of larvae in the patients' muscle biopsies by histology and/or PCR. The ensuing investigation traced the wild boar meat back to Spain. Several batches of imported wild boar meat were recalled but tested negative. The public health investigation allowed us to identify clustered undiagnosed cases. Early warning alerts and a coordinated response remain indispensable at a European level.

[Assessment of transmammary transmission of Trichinella patagoniensis in BALB/c mice]. / Evaluación de la transmisión galactógena de Trichinella patagoniensis en ratones BALB/c.

Since 1916 to date, it has been suspected that vertical transmission of parasites from the genus Trichinella could occur in pregnant or lactating women during the parenteral phase of infection. The aim of the present study was to evaluate the transmammary transmission of T. patagoniensis in BALB/c mice. Twenty 7-week-old BALB/c mice were distributed into two groups of 10 individuals each, depending on the time of gestation when they were infected, 15 or 18 days after detection of the vaginal plug. Each group was subdivided into two subgroups of 5 mice each, which were given an oral dose of 100 or 500 infective larvae respectively. Euthanasia and subsequent artificial digestion was performed in the pups and the dams. No T. patagoniensis L1 larvae were found in any of the offsprings analyzed. The observed results suggest that vertical transmission of T. patagoniensis would not be possible in BALB/c mice.

Outbreak of trichinellosis due to wild boar meat and evaluation of the effectiveness of post exposure prophylaxis, Germany, 2013.

BACKGROUND: Food safety authorities discovered that wild boar meat products contaminated with Trichinella spiralis had entered the food chain in Germany in March 2013. Public health authorities issued guidelines for health professionals including post-exposure prophylaxis (PEP) using mebendazole and advised the public to seek medical advice if exposed. Our objective was to identify factors associated with the development of trichinellosis and to evaluate post exposure prophylaxis. METHODS: Persons who reported to local public health departments as exposed were interviewed concerning exposure, symptoms, and medication. Serum samples were tested by an in-house Trichinella-specific enzyme-linked innunosorbent assay. Cases were defined as persons presenting with myalgia and/or periorbital edema and Trichinella-specific immunoglobulin M and immunoglobulin G antibodies after exposure to implicated products. RESULTS: Of 101 persons interviewed, 71 were exposed and serologically tested. Antibodies were detected in 21/71 (30%) and 14/71 (20%) met the case definition. Attack rates were positively correlated to the amount of implicated product consumed. Among n = 37 persons who received anthelmintics as PEP, 6 persons developed trichinellosis. These cases exclusively occurred among persons starting PEP 6 days or later post-exposure. Exposure to implicated products and delaying PEP were also significantly associated with developing trichinellosis (P < .01) in a multivariable analysis. CONCLUSIONS: Concerted efforts by food safety and public health authorities lead to timely outbreak control and facilitated the provision of early PEP. PEP appears to be effective in preventing trichinellosis when given early, preferably within 6 days. We therefore recommend initiating PEP without delay in similar settings and encourage public health professionals to fast-track this intervention.

The immature stages of Dermestes maculatus, Sarcophaga sp. and Phaenicia sericata as potential paratenic hosts for Trichinella spiralis in nature.

The role of some insect populations in the transmission of Trichinella sp. has been demonstrated. However, most of the studies have been conducted under controlled conditions which may influence the real role that they could play as a paratenic host in nature. To enlight this issue, a series of studies to determine the infective capability of the muscle larva of Trichinella spiralis recovered from immature stages of insect populations that fed on infected tissues exposed to natural conditions were carried out. Mice harbouring T. spiralis muscle larvae (ML) were sacrificed and deposited on a pitfall trap which was established in an open and safe area through 25 days in summer. Necrophilous and necrophagous insects that fed on corpses were recovered, identified and processed to search for live ML of T. spiralis. A complementary study in which maggots of Dermestes maculatus recovered from nature were induced to feed on muscle tissues harbouring T. spiralis larvae was also performed. The muscle larvae recovered from insects at different times of exposition were counted and inoculated to mice to determine the reproductive capability index (RCI). At day 3 of exposition, 29 live ML of T. spiralis were recovered from maggots of Phaenicia sericata. The RCI for these larvae was 133.6. On day 5 of exposition, maggots of Sarcophaga sp. were identified and 17 live T. spiralis larvae were recovered; the RCI of these larvae was 43.4. The T. spiralis ML recovered from maggots of D. maculatus obtained after 2 days of feeding on experimentally infected tissue showed a RCI of 24. The results suggest that larval stages of P. sericata, Sarcophaga sp. and D. maculatus might have an important role as a paratenic host of T. spiralis, which, in terms, may influence the epidemiology of this nematode in endemic areas of trichinellosis.

[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.

[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.

[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.

[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.

Worldwide occurrence and impact of human trichinellosis, 1986-2009.

To assess the global incidence and clinical effects of human trichinellosis, we analyzed outbreak report data for 1986-2009. Searches of 6 international databases yielded 494 reports. After applying strict criteria for relevance and reliability, we selected 261 reports for data extraction. From 1986 through 2009, there were 65,818 cases and 42 deaths reported from 41 countries. The World Health Organization European Region accounted for 87% of cases; 50% of those occurred in Romania, mainly during 1990-1999. Incidence in the region ranged from 1.1 to 8.5 cases per 100,000 population. Trichinellosis affected primarily adults (median age 33.1 years) and about equally affected men (51%) and women. Major clinical effects, according to 5,377 well-described cases, were myalgia, diarrhea, fever, facial edema, and headaches. Pork was the major source of infection; wild game sources were also frequently reported. These data will be valuable for estimating the illness worldwide.

[Monitoring of animal trichinellosis in the Czech Republic--the past and present]. / Monitoring trichinelózy zvírat v Ceské republice--historiea soucasnost.

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.

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.

Animal welfare and zoonosis risk: anti-Trichinella antibodies in breeding pigs farmed under controlled housing conditions.

BACKGROUND: Domesticated pigs are the main source of Trichinella sp. infections for humans, particularly when reared in backyards or free-ranging. In temperate areas of southern Europe, most pigs are farmed under controlled housing conditions, but sows and sometimes fattening pigs have access to outdoors to improve animal welfare. The aim of the present study was to investigate whether outdoor access of breeding pigs farmed under controlled housing conditions can represent a risk for Trichinella sp. transmission when the farm is located in an agricultural area interspersed with wooded areas and badlands, where Trichinella spp. could be present in wildlife. METHODS: Serum samples were collected from 63 breeding sows and one boar before and after their access to an open fenced area for 2 months and from 84 pigs that never had outdoor access. Samples were screened for anti-Trichinella antibodies by ELISA, and positive sera were confirmed using Western blot (Wb) excretory/secretory antigens. To detect Trichinella sp. larvae, muscle tissues from serologically positive and negative pigs were tested by artificial digestion. RESULTS: Thirteen (20.6%) sows and one boar tested positive with both ELISA and Wb. No larvae were detected in muscle samples of serologically positive and serologically negative pigs. Positive serum samples were then tested by Wb using crude worm extract as antigens. The Wb banding pattern displayed was that characteristic of encapsulated species (Trichinella spiralis or Trichinella britovi). CONCLUSIONS: The detection of anti-Trichinella antibodies without larvae in the pig muscles, supported by epidemiological data, suggests that pigs may have been exposed to T. britovi. This study stresses the importance of instigating monitoring systems at farm level to prevent Trichinella sp. transmission and to investigate, through a landscape parasitological study, the suitability of a site before the planting of a high containment level pig farm in which the sows can have outside access to improve their welfare during pregnancy.

Early detection by polymerase chain reaction of migratory Trichinella spiralis larvae in blood of experimentally infected mice.

We studied the sensitivity of polymerase chain reaction (PCR) for detecting DNA of migratory larvae of Trichinella spiralis at an early stage of infection with this parasite. We derived primers for PCR from a 1.6-kb repetitive sequence of the genome of T. spiralis and used PCR to detect Trichinella-specific DNA in blood of mice infected with 20, 100, or 300 muscle-derived larvae of T. spiralis at 3-21 days postinfection (dpi). We detected T. spiralis DNA in blood of mice infected with 20 larvae at 5 and 6 dpi, with a detection rate of 7.69% and in blood of mice infected with 100 larvae at 5-12 dpi, with a peak detection rate of 38.46% at 7 dpi. PCR detected T. spiralis larvae at 5-17 dpi in mice infected with 300 larvae, with detection rates exceeding 50% from 5 to 10 dpi and a peak rate of 61.54% at 7 dpi. The detection rates of T. spiralis larvae with PCR in the three groups of mice showed an increasing trend with an increase in the infecting dose of larval parasites (F = 17.811, p < 0.01). Our findings indicate that the sensitivity of PCR for detecting DNA migratory larvae of T. spiralis in blood of mice infected with this parasite depends on the severity of infection and the time elapsed after infection, and suggest that PCR may be useful for detecting Trichinella infection at an early stage in humans and food animals that test negatively for anti-Trichinella antibodies.