Human Trichinellosis Research Articles

Outbreak of human trichinellosis in Northern California caused by Trichinella murrelli.

In October of 2008, an outbreak of trichinellosis occurred in northern California that sickened 30 of 38 attendees of an event at which meat from a black bear was served. Morphologic and molecular testing of muscle from the leftover portion of bear meat revealed that the bear was infected with Trichinella murrelli, a sylvatic species of Trichinella found in temperate North America. Clinical records revealed a high attack rate for this outbreak: 78% for persons consuming any bear meat and 100% for persons consuming raw or undercooked bear meat. To our knowledge, this report is the first published report of a human trichinellosis outbreak in the United States attributed to T. murrelli, and it is the second such outbreak reported worldwide.

An outbreak of trichinellosis in Hungary

In a small village of Hungary, a human trichinellosis outbreak (affecting eight people) occurred in January-February, 2009. In the outbreak investigation (i) Trichinella spiralis larvae were detected in meat products derived from the pigs slaughtered in the backyard of one of the patients (a foxhunter) in December 2008, and in a brown rat captured in the same backyard; (ii) sera of 24 pigs held in 11 yards of the village and that of some dogs of the foxhunter were found Trichinella-positive; (iii) sera of five villagers who could not be infected in the particular outbreak were also found reactive in Trichinella-specific laboratory tests. The followings helped the rise of an outbreak: the geographical position and the presence of empty houses favoured the multiplication of rats; there was no extermination of rats in the previous years; there was no meat inspection; raw meat and improperly processed meat products were tasted at the pig-slaughter; villagers gave tastes to each other. People were informed on the symptoms, the way of transmission, and the possibilities of prevention of trichinellosis by experts. With the help of local authorities, all the properties including the grounds with empty houses were involved in the extermination of rodents.

Detection and Zoonotic Potential ofTrichinellaspp. from Free-Range Pig Farming in Greece

Trichinellosis is a serious parasitic zoonosis, which is widely distributed around the world. Pork meat is still the predominant source of outbreaks of human trichinellosis in many countries. The aim of this study is to examine the impact of Trichinella spp. as an important risk factor on the free-range pig farming sector in Greece. In 2009, during routine testing for the detection of Trichinella larvae at slaughterhouses and the National Reference Laboratory for Parasites (NRL), a total of 826,426 pigs were tested with the magnetic stirrer method for Trichinella spp. at slaughterhouses, including 2,892 samples from free-range pigs. Two positive samples were detected: one positive for Trichinella britovi and one positive for Trichinella spp. (unspecified) in the samples from wild farmed free-range pigs. It is alarming that one of these cases was connected with clinical signs of trichinellosis in five persons of the same family in northeastern Greece, who consumed undercooked pork meat from a free-range pig farm. During 2010, a total number of 1,295,034 pigs were tested with same method, including 4,159 samples from free-range pig farms. Five positive samples for Trichinella spp. (unspecified) were detected from 4,159 free-range pigs tested by the Greek NRL. Moreover, 363 serum samples from free-range pigs were serologically tested with enzyme-linked immunosorbent assay (ELISA). Moreover, 363 serum samples from farmed free-range pigs were serologically tested with ELISA, and 15 samples were found positive. Finally, the present study is the first report of detection of T. britovi in Greece. In conclusion, based on the results of the present study, Trichinella spp. is a high-risk factor for the free-range pig farming in Greece.

Trichinellosis in developing countries: is it neglected?

Trichinellosis is a foodborne zoonosis caused by the parasitic nematode Trichinella, which is characterized by an extremely wide host range and geographical distribution. The aim of the present review is to provide epidemiological information on animal and human trichinellosis occurring in developing countries in the different continents, where cooking habits along with poverty and poor sanitary conditions and lack of veterinary controls may facilitate the occurrence of human trichinellosis outbreaks. Countries have been considered according to the six regions designated by the World Health Organization (WHO): 1) WHO African Region, 2) WHO Region of the Americas, 3) WHO South-East Asia Region, 4) WHO European Region, 5) WHO Eastern Mediterranean Region, and 6) WHO Western Pacific Region. For the purposes of this article, developing countries are defined as those not industrialised according to the World Economic Outlook Report of the International Monetary Fund (http://www.imf.org); however, with regard to the European Region of WHO, only those countries that are not member states of the European Union will be considered.

Development of a single larva microsatellite analysis to investigate the population structure of Trichinella spiralis

Trichinella spiralis is the most important etiological agent of human trichinellosis. It has a cosmopolitan distribution and is transmitted to humans mainly through the consumption of pork. In nature, transmission occurs among animals through the ingestion of an infected carcass by one or more hosts. Microsatellite markers have provided insight into how T. spiralis dispersed geographically over its evolutionary history. The objectives of the present study were to develop microsatellite markers capable of differentiating single larvae for investigating the inter- and intra-specific population structure of T. spiralis and to determine their usefulness as genetic markers to study transmission mechanisms of this zoonotic parasite. A panel of 48 larvae derived from each of 22 distinct isolates originating from the Americas, Asia and Europe, were investigated. A total of 27 alleles were detected in these samples using seven new markers. The sequences of the amplified fragments containing the microsatellites support the homology of the amplified products and validate their use for genetic population studies. We documented the first known occurrence of a genetically variable larval admixture, indicating that more than two adults gave rise to the ensuing population of this host’s muscle larvae. Globally, T. spiralis was observed to harbor less genetic variation than other nematodes, a result consistent with previous assays of nuclear and mitochondrial variation.

Trichinellosis in hospitalized patients from a Romanian endemic area, 2007–2009

Trichinellosis continues to represent a major concern in Romania, a country that, over the years, has had favourable conditions for the transmission and maintenance of this disease. During the years 2007–2009, Romania has reported to the WHO's Regional Office for Europe the highest incidence of trichinellosis in humans. This study was aimed at analysing the epidemiological, clinical, laboratory and therapeutic aspects of trichinellosis in a well-known Romanian endemic area, and at determining the particular aspects of this disease in children and the adult population. We retrospectively investigated the medical records of patients from two western Romanian counties, diagnosed with trichinellosis and hospitalized between 2007 and 2009. During this period, a total of 91 persons presented with this disease, and the corresponding yearly average incidence was 2.7 cases per 100 000 inhabitants. Patients were aged 3–80 years (mean age 33.3 ± 17.9 years), and most of them were adults (78%). Males accounted for 51.6% of cases. Unemployed adults belonging to the gypsy minority predominated within the study group (46.5%). Myalgia, fever and oedema were the most common symptoms. The mean eosinophil count was 25.1% ± 17.1% (range 1–75.8%), and was significantly higher in adults than in children. All patients were treated with albendazole, and 52.7% had associated corticotherapy. Trichinellosis is still probably the most important parasitic disease in Romania. Recent reports have revealed inadequate application of prophylactic and control measures against this disease. Consequently, public health strategies should be reconsidered, and more efficient and rigorous education of the population is required.

A 12-year-old child with trichinellosis, pyomyositis and secondary osteomyelitis

Trichinellosis is a parasitic infestation affecting the skeletal muscles. Cases of trichinellosis in humans have been reported from most regions of the world. However, a review of literature revealed only two reported cases of human trichinellosis in India. Further, a diagnosis of superimposed pyomyositis in trichinellosis with secondary osteomyelitis has not been reported to our knowledge. This article reports this rare case presentation in a 12-year-old child. Timely intervention helped prevent long-term morbidity in our patient. In our case report, we also discuss in detail the pathogenesis of such a condition and discuss the role of imaging modalities and an early magnetic resonance imaging (MRI) to diagnose the condition and start an early treatment.

A Modern Understanding of a Historical Parasite: Food-Borne Risks of Trichinella from California Bear and Feral Pig Populations

Trichinellosis is a zoonotic disease caused by one of the most widely distributed parasite groups in the world, Trichinella. Infection and illness in humans occurs following the consumption of undercooked meat containing larvae. Many cases of trichinellosis go unreported, but symptomatic disease can present with nausea, diarrhea, vomiting, fatigue, and in severe cases, death. Since the eradication of Trichinella from the commercial swine industry, wildlife meat, specifically black bear and feral pig, has become the main cause of human trichinellosis in the United States. California continues to be home to the majority of these cases. Despite this change in epidemiology, few studies have focused on importance of wildlife as a reservoir of human trichinellosis. The most recently reported prevalence estimate of Trichinella in California black bears was over 30 years ago, in 1977. To our knowledge, there have been no published reports on the prevalence of Trichinella in California feral pigs. Furthermore, human, black bear, and feral pig population growth, coupled with increased urban development, has created an expanding ecological niche for parasite transmission, thus increasing the risk of Trichinella infection for consumers of wildlife meat. Given the lack of contemporary data and knowledge, there is a need to generate estimates of the current burden of Trichinella in California wildlife in order to assess the foodborne risk this potentially lethal parasite poses to the public.

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.

Differential detection of Trichinella papuae, T. spiralis and T. pseudospiralis by real-time fluorescence resonance energy transfer PCR and melting curve analysis

Trichinellosis caused by nematodes of Trichinella spp. is a zoonotic foodborne disease. Three Trichinella species of the parasite including Trichinella spiralis, Trichinella papuae and Trichinella pseudospiralis, have been etiologic agents of human trichinellosis in Thailand. Definite diagnosis of this helminthiasis is based on a finding of the Trichinella larva (e) in a muscle biopsy. The parasite species or genotype can be determined using molecular methods, e.g., polymerase chain reaction (PCR). This study has utilized real-time fluorescence resonance energy transfer PCR (real-time FRET PCR) and a melting curve analysis for the differential diagnosis of trichinellosis. Three common Trichinella species in Thailand were studied using one set of primers and fluorophore-labeled hybridization probes specific for the small subunit of the mitochondrial ribosomal RNA gene. Using fewer than 35 cycles as the cut-off for positivity and using different melting temperatures (Tm), this assay detected T. spiralis, T. papuae and T. pseudospiralis in muscle tissue and found the mean Tm±SD values to be 51.79±0.06, 66.09±0.46 and 51.46±0.09, respectively. The analytical sensitivity of the technique enabled the detection of a single Trichinella larva of each species, and the detection limit for the target DNA sequence was 16 copies of positive control plasmid. A test of the technique's analytical specificity showed no fluorescence signal for a panel of 19 non-Trichinella parasites or for human and mouse genomic DNA. Due to the sensitivity and specificity of the detection of these Trichinella species, as well as the fast and high-throughput nature of these tools, this method has application potential in differentiating non-encapsulated larvae of T. papuae from T. spiralis and T. pseudospiralis in tissues of infected humans and animals.

Atypical trichinellosis without eosinophilia associated with osteomyelitis

Human trichinellosis is an important food-borne zoonosis caused by a nematode worm, Trichinella. The symptoms of the disease vary widely depending on the infection load, stage of infection and host immunity and include nausea, vomiting, abdominal pain, fever, facial edema and muscle pain. The disease is usually characterized by moderate to high eosinophilia. We hereby discuss an atypical case of trichinellosis, which presented with myositis of the thigh muscles but had no eosinophilia and no facial or periorbital edema and was associated with osteomyelitis of the femur. The diagnosis was made by the demonstration of anti-trichinella antibodies and later confirmed by the presence of larvae of Trichinella in the digested muscle biopsy. Physicians must be aware of trichinosis and should include it in their differential diagnosis when examining patients with fever and myositis with or without eosinophilia.

Strayed dogs sentinels ofTrichinella britoviinfection in Kosovo

Strayed dogs sentinels of<i>Trichinella britovi</i>infection in Kosovo

Efficacy of Lasia spinosa leaf extract in treating mice infected with Trichinella spiralis

Trichinellosis is a widespread zoonoses for which no effective drug treatment is available at this time. Though anthelmintics such as mebendazole and albendazole are commonly used to treat human trichinellosis, none of these drugs are fully effective against the encysted or new-born larvae of Trichinella spiralis. In recent years, there has been a growing interest in developing newer anthelminthics from medicinal plants, particularly the ones used in traditional medicines in many parts of the world, due to the increasing spread of anthelminthic resistance and/or decreasing activity against encapsulated larval stages of parasites. The aim of the present study was to investigate the efficacy of leaf extract of Lasia spinosa (Araceae) against different life cycle stages of T. spiralis, i.e. adult (days3 and 4 post-infection), migrating larvae (days8, 9 and 10 post-infection) and encysted muscle larvae (days31-37 post-infection). The study showed that L. spinosa leaf extract is effective against all the three life cycle stages of parasite. Against the adult stage, an oral administration of plant extract at 800mg/kg dose revealed a 75.30% reduction in the number of adult worms, as compared to untreated controls at day10 post-infection. Whereas against migrating larvae, the same dose of plant extract given for 3days, reduced the number of larvae recovered from musculature of treated animals by 72.23%. However, in comparison of preceding two stages, the extract showed comparatively less efficacy against the encysted larvae of parasite. In this case, the 800mg/kg dose of extract given for 7days (after 30day of post-infection) revealed only 64.84% reduction in the number of encysted larvae, as was evident from larval count on day49 post-infection. Therefore, the results of this study indicate that leaf extract of L. spinosa possesses significant anthelminthic efficacy against the adult stages and migrating larvae of T. spiralis. On the other hand, the encysted muscle larvae of parasite are comparatively less sensitive to L. spinosa leaf extract treatment.

Reviews on Trichinellosis (IV): Hepatic Involvement

Trichinella sp. larvae are released from the intestine and usually migrate through the liver into the general circulation. Nevertheless, hepatic involvement does not represent a leading feature of human trichinellosis. This narrative systematic review focuses exclusively on hepatic complications of trichinellosis and includes a brief overview and analysis of selected cases reported in the literature. Our major goals were to gather important data to understand the substrate of trichinous liver injury and to provide helpful clinical hints for practitioners. To our knowledge, this is the first international review dedicated to this topic. Thirty two cases were detailed enough to allow pooled analysis. The mean age of the analyzed group was 30.5±17 years old with most cases aged 19 to 29 years (29%). Hepatomegaly was noticed in 34.4% of cases, hypoalbuminemia in 40.6%, and hypoproteinemia in 34.4%. Our systematic analyses demonstrated that hepatic complications were mainly evidenced in fatal cases of trichinellosis (65.6%). The most frequent necroptic findings were parenchymatous and/or fatty degeneration of the liver (59.4%). Although less discussed in the literature than other complications, hepatic involvement should be considered more carefully because of its significant consequences on protein metabolism and liver function. Difficult to be revealed intra vitam, hepatic involvement may represent an additional concern to the classical clinical picture of trichinellosis and other life-threatening complications, especially in severe cases of infection. Consequently, physicians should be aware of any possible liver involvement to ensure adequate management of their patients.

Human beings are highly susceptible to low doses of Trichinella spp.

Trichinella is an important foodborne pathogen causing considerable morbidity and mortality. To prevent human trichinellosis, meat inspection for Trichinella spp. at slaughter is a key instrument. Current testing is based on minimal infectious dose in humans, but a scientific basis for this approach is lacking. To this end, a dose-response model must be developed, allowing translation of exposure into disease burden at the population level. We developed novel methods for dose-response assessment using outbreak data incorporating sexual reproduction of the parasite. A selection of suitable outbreak studies, reporting numbers exposed and infected, as well as estimated doses, was collated from a literature study. Humans appear to be highly susceptible: exposure to low doses (few larvae) is associated with a considerable risk of infection. As a consequence, levels of Trichinella in meat must be low to maintain acceptable health risks.

Exotic imported travel-related infections in Japan

Human social and economic activities as well as changes in the global environment are responsible for outbreaks of emerging and re-emerging infectious diseases. We have encountered 5 cases of asymptomatic schistosomiasis in Japanese travelers who were exposed to cercariae-contaminated freshwater in east Africa. Because all 5 travelers showed normal results upon their return medical examination, Schistosoma, which is not indigenous to Japan, was unfortunately not suspected as the causative agent of this chronic and silent infection. In addition, in 2008, we experienced 2 Japanese cases in an exotic and local pandemic of human trichinellosis which was associated with eating raw soft-shelled turtles in Taiwan. The cause of this emerging pandemic can be attributed to the traditional custom of eating raw soft-shelled turtles. It is important for all travelers to understand that anyone at anytime can be exposed to the threat of a pandemic; therefore, the first step for all travelers is to be aware of worldwide endemicity and keep up to date on the infectious diseases that are prevalent. Concurrently, it is important to identify the presence of slowly and silently expanding infectious diseases and establish surveillance systems to detect not only serious emerging infectious diseases but also chronic and silent infections.

The draft genome of the parasitic nematode Trichinella spiralis

Genome-based studies of metazoan evolution are most informative when phylogenetically diverse species are incorporated in the analysis. As such, evolutionary trends within and outside the phylum Nematoda have been less revealing by focusing only on comparisons involving Caenorhabditis elegans. Herein, we present a draft of the 64 megabase nuclear genome of Trichinella spiralis, containing 15,808 protein coding genes. This parasitic nematode is an extant member of a clade that diverged early in the evolution of the phylum enabling identification of archetypical genes and molecular signatures exclusive to nematodes. Comparative analyses support intrachromosomal rearrangements across the phylum, disproportionate numbers of protein family deaths over births in parasitic vs. a non-parasitic nematode, and a preponderance of gene loss and gain events in nematodes relative to Drosophila melanogaster. This sequence and the panphylum characteristics identified herein will advance evolutionary studies and strategies to combat global parasites of humans, food animals and crops.

An epidemiological overview of swine trichinellosis in China

Trichinellosis is a major food-borne zoonosis with health, social, and economic impacts. Epidemiological data on swine trichinellosis in China from 2005 to 2009 were obtained from seven Provinces/autonomous regions/Municipalities (P/A/M) and analyzed and sero-epidemiological data were acquired from five P/A. The seroprevalence ranged from 0.01% to 29.95% as determined by enzyme-linked immunosorbent assay or an immunochromatographic strip method. The prevalence of Trichinella infection in swine slaughtered at abattoirs varied from 0% to 5.75% in five P/A. Between 2005 and 2009, endemic areas of swine trichinellosis were located mainly in the Western (Guangxi and Qinghai), central (Henan and Hubei), and North-eastern parts (Heilongjiang) of China. Swine trichinellosis in China is transmitted mostly through garbage. Pigs infected with Trichinella are predominately from small backyard farms where animals are raised under poor hygienic conditions, and from rural and mountainous areas where they range freely at pasture. The prevalence of Trichinella in pork sold at the market was reported in four P/A, and varied from 0.06% to 5.6% as determined by trichinoscopy or the digestion method. From 2005 to 2009, 15 outbreaks of human trichinellosis, with 1387 cases and 4 deaths, were recorded in three P/A of South-western China. Twelve (85.71%) of these 15 outbreaks were caused by the eating of raw or undercooked pork, which remains the predominant source of trichinellosis in humans. Pig-rearing practices must be improved, and mandatory inspection of pork further strengthened in rural and mountainous areas in Western China for the control of the disease.

Investigation on a focus of human trichinellosis revealed by an atypical clinical case after wild-boar (Sus scrofa) pork consumption in northern Italy

Trichinellosis is one of the most serious foodborne parasitic zoonoses in Europe. Wild carnivorous and omnivorous hosts are the main reservoirs of Trichinella spp. nematodes in nature. In the winter of 2008-2009, an atypical clinical case of trichinellosis occurred for the consumption of pork from a wild boar (Sus scrofa) hunted in southwestern Alps in Italy. The symptomatic individual showed delayed development of oedemas in the lower limbs and eosinophilia, which appeared three months after infection. Muscle samples harboured 3.8 larvae/g, which were identified as Trichinella britovi. During the epidemiological investigation, anti-Trichinella IgG were detected in five hunters.

Trichinellosis epidemics in AP Vojvodina in the period 2000-2009

In the observed decade, 1300 cases of trichinellosis were registered in Vojvodina, including three with a lethal outcome. The lethality was 0.23%. The incidences of trichinellosis ranged from 2.2/100,000 to 13.6/100,000. The rate of incidence depends both on the number of epidemics and the size of the epidemic reported in a year. Most incidences were reported in 2002 and 2005, as a consequence of the spread of trichinellosis through the purchase of infested food. The epidemic of trichinellosis in the Middle Banat district that started at the end of 2001 is considered to be the largest outbreak of human trichinellosis in Vojvodina, when 313 people got sick. In most of the cases the affected people reported they had eaten smoked sausages. The high incidence of trichinellosis in 2005 was a consequence of three thrichinellosis outbreaks that had been spreading through infested smoked sausages originating from illegal production and trade. More than 200 cases of trichinellosis were reported in Vojvodina. Today, Srem is still considered a hyperendemic area, because more than 30% of all the epidemics occur in this area. The available data indicate that trichinellosis is spread all over Vojvodina and that the absence of control results in the risk from the incidence of human trichinellosis. In many European countries the epidemiological situation is stable, but in our country trichinellosis is the most important zoonotic disease. This unstable epidemiological situation is the consequence of the widespread infection, culinary customs, and the fact that there is inadequate control of meat and meat products in households and illegal trade.