A trichinosis outbreak among Southeast Asian refugees

Systematics and epidemiology of trichinella

In this review, we describe the current knowledge on the systematics, ecology and epidemiology of Trichinella and trichinellosis, and the impact of recent research discoveries on the understanding of this zoonosis. The epidemiology of this zoonosis has experienced important changes over the past two decades, especially with regard to the importance of the sylvatic cycle and the sylvatic species. Outbreaks of trichinellosis due to Trichinella spiralis from domestic swine, while still frequent, increasingly are caused by other Trichinella spp. infecting hosts such as horses, dogs, wild boars, bears and walruses. The latter revelations have occurred as a result of a series of discoveries on the systematics of Trichinella spp., facilitated by new molecular tools. As a consequence, the genus is now composed of two clades, an encapsulated group (five species and three genotypes) and a non-encapsulated one (three species). This has sparked renewed investigations on the host range of these parasites and their epidemiological features. Most dramatic, perhaps, is the recognition that reptiles may also serve as hosts for certain species. This new knowledge base, in addition to having an important relevance for food safety policies and protection measures, is raising important questions on the phylogeny of Trichinella spp., the ecological characteristics of the species and their geographic histories. Answers to these questions may have great value for the understanding of the evolutionary biology for other parasitic helminths, and may increase the value of this genus as models for research on parasitism in general.

A trichinellosis outbreak in Borikhamxay Province, Lao PDR

Trichinellosis is documented in Southeast Asia, particularly in Thailand and China. Data from Lao PDR are lacking. An outbreak investigation was conducted in Borikhamxay Province after three patients with suspected trichinellosis consulted the Mahosot Hospital, Vientiane. In total, 22 trichinellosis cases were identified; 21 cases could be confirmed by Western blot. High fever (100%), muscle pain (91%), upper eyelid oedema (86%) and diarrhoea (59%) were observed. Among the 22 patients, 86% had consumed pork meat from the same source. This is the first report of an outbreak investigation in Lao PDR since 1975. It shows that the incidence of trichinellosis is much higher than currently thought.

Outbreak of suspected trichinosis among travelers returning from a neighboring island

BACKGROUND

An outbreak of trichinosis involving a cohort of 33 returning travelers from a resort island in a neighboring country was suspected, beginning with 2 initial cases who were hospitalized with a syndrome of fever, myalgia and eosinophilia.

METHOD

At the initial visit, a full history was obtained and a physical examination was performed for each individual. Also, blood was drawn for full blood count, blood film for malaria parasites and Trichinella serology. Extensive epidemiological investigations identified a total of 84 returning travelers from 6 separate groups, of which 58 (69%) were subjected to a detailed interview, including the kinds of meat consumed on the island.

RESULTS

Twenty-five of these 33 persons (75.7 %) fulfilled clinical or serological case definition criteria for trichinosis. IgG antibody for Trichinella spiralis was detected in 8 out of 32 persons who had the test done (25%). Symptoms were generally mild, with only one patient (3%) requiring steroids for prolonged myositis.

CONCLUSION

We suspect this outbreak to be due to trichinosis although the source could not be identified. Extensive epidemiological investigations identified a total of 84 returning travelers from 6 separate groups, of which 58 (69%) were subjected to a detailed interview, including the kinds of meat consumed on the island, but the source of the outbreak could not be identified.

Seroprevalence of Trichinella infection in domestic swine based on the National Animal Health Monitoring System's 1990 and 1995 swine surveys

Swine sera collected by the US Department of Agriculture's Center for Animal Health Monitoring during 1990 and 1995 was tested for antibodies to Trichinella spiralis using an enzyme immunoassay. From a total of 3048 sera collected from lactating sows in 1990, five sera tested positive for a prevalence of 0.16%. From a total of 7987 sera collected from both finishing pigs and gestating sows in 1995, one serum was positive for a prevalence of 0.013%. Responses to questionnaires administered at the time of serum collection showed that seropositive farms had management variables consistent with known risk factors for exposure to trichinae.

Clinical aspects of infection with Trichinella spp

Isolated cases and outbreaks of infection with Trichinella spp. occur frequently throughout the world, sometimes resulting in fatalities. The clinical presentations of signs and symptoms are remarkably constant for most of the species of Trichinella, but in infections with Trichinella nativa and Trichinella britovi, classical symptoms of trichinellosis may be absent. It is important to be able to correlate the clinical presentation of trichinellosis with the life cycle of these helminths in order to make an accurate diagnosis. Knowledge of the epidemiology of the disease enables the physician to identify other potential cases, since most epidemics can be traced back to a common source of raw or undercooked meat. A comprehensive summary relating the most important clinical variables is presented graphically for easy reference to the text. Symptoms and signs are considered in relation to severity of infection. Laboratory findings and diagnostic techniques, including new modalities (e.g., DNA and antigen detection), are discussed. A discussion of treatment and preventive measures concludes our review.

Trichinosis

Preview The incidence of many infectious diseases has declined as a result of modern sanitation, disease surveillance programs, and other public health measures. Trichinosis, however, continues to occur at a frequency that merits awareness by physicians. Dr Stack describes a case linked to homemade pork sausage and reviews current factors in epidemiology, diagnosis, and treatment of this uncommon but still troublesome disease.

Trichinosis: infrequent diagnosis or frequent misdiagnosis?

Trichinosis, a disease of wild and domestic animals caused by the nematode Trichinella spiralis, is an infrequently diagnosed infection in human beings. We present the case of a 33-year-old man with trichinosis whose diagnosis was complicated by the presence of maxillary sinusitis.