Table 1.
Historical landmarks concerning Trichinella and trichinellosis with particular reference to studies at USDA laboratories (in bold).
| Year | Contribution | Reference |
|---|---|---|
| 1835 | Trichina spiralis discovered and described based on cysts found by a British first- year medical student, James Page, while dissecting a human cadaver that had died of tuberculosis. | Owen (1835); history detailed by Campbell (1979) |
| 1842 | T. spiralis detected in a human cadaver in the USA. | Bowditch (1842) |
| 1846 | Trichina found in pork that the 23-year-old human physician, Joseph Leidy was having for dinner; cooked pork contained dead larvae. | Leidy (1846); details provided by Ward (1923) |
| 1850 | Experimental transmission of Trichina in animals. Trichina were found in muscles of a pet badger that had been fed scraps of muscles from dogs and cats naturally infected with trichina. Three pups fed muscles of badger died of trichinosis. | Herbst (1853): full account in Reinhard (1958) |
| 1857 | Trichina from human flesh found infective to mice, dogs, and pigs. Morphology of adult T. spiralis described. | Leuckart (1860); details in Campbell (1983) |
| 1859 | Trichina from human flesh was infective to a dog and pig. Development of T. spiralis first described, and trichinoscopic testing of pigs at slaughter proposed to monitor infections in pigs. | Virchow (1859); details in Campbell (1983) |
| 1860 | A previously healthy 20-year-old female servant who ate and served pork at the Christmas dinner to a farmer family in Germany died of acute trichinosis; an autopsy performed by Zenker identified thousands of trichina in her muscles. Zenker found adult T. spiralis in intestines of this woman that had been in cold storage for 1 month. The farmer and his wife also had died. Two months later, Zenker visited the butcher who prepared ham and sausages sold to the farmer. The butcher also developed severe muscle pains but survived. Zenker found trichinae in ham and in pork sausages that had been stored at the butcher shop for about 2 months. First demonstration of human as an intermediate and definitive host for T. spiralis. | Zenker (1860); full account in Reinhard (1958) |
| 1863–1879 | Mandatory inspection of pork introduced in Germany. In trichinoscope method around 28 or more samples in 2 rows of wheat grain sized diaphragmatic muscle are arranged on a glass slide and compressed under another slide, clamped with screws, and examined in a projection microscope; illustrated by Gould (1970) and Zimmermann (1983). The procedure cannot detect light infections (1 larva/g). | Zimmermann (1983); Gould (1970); Brantz (2008) |
| 1879–1888 | Several European countries banned importation of pork from USA. | Gignilliat (1961) |
| 1891 | Trichinoscopic testing of pork for export introduced in USA. In 8 years of testing (1898–1906) of > 8 million pigs for export to Germany tested, trichina was found in 1.41%. | Hall (1937) |
| 1895 | Trichinosis outbreaks observed in Germany, some involving 100 cases at a time. | Kozar (1970) |
| 1895 | Amended name Trichina to Trichinella because the genus Trichina was preoccupied with flies. Henceforth, the parasite was recognized as Trichinella spiralis (Owen, 1835) Railliet, 1895. | Railliet, 1895, Railliet, 1896 |
| 1897 | Artificial digestion of pork in pepsin and hydrochloric acid proposed to liberate encysted larvae from muscle. Trichinella first found in horse meat. | Thornbury (1897) |
| 1898 | The USDA's Bureau of Animal Industries posts C.W. Stiles, an eminent American parasitologist, to the Embassy in Berlin to test German claims that American pork was the source of outbreaks of trichinellosis in Germany. | Stiles (1901); Cassedy (1971) |
| 1911 | First serological diagnosis test (complement fixation test) described. | Ströbel (1911) |
| 1914, 1990,2009 | Demonstration that freezing kills Trichinella in pork, including different Trichinella species (genotypes) circulating in USA. Freezing standards proposed for meat industry (Kotula et al., 1990) | Ransom (1914); Ransom (1915); Ransom (1916); Kotula et al. (1990) |
| 1919,1939, 1983 | Heating to 58oC kills trichina in pork. Only dead larvae were found in sausages heated to 58 °C (137 °F). Time and temperatures parameters established for FSIS byKotula et al. (1983). | Ransom and Schwartz (1919); Schwartz (1939); Schwartz (1929); Kotula et al. (1983) |
| 1920, 1985 | Demonstration that irradiation kills Trichinella in pork.Brake et al. (1985)tested consumer acceptable levels of gamma irradiation. | Schwartz (1921); Brake et al. (1985) |
| 1920, 2017 | Curing of pork can kill Trichinella. Combining NaCl concentrations above 1.3% with fermentation to pH 5.2 or below inactivates > 96% of Trichinella muscle larvae in stuffed sausages within 24–28 h. | Ransom et al. (1920); Schwartz, 1939, Schwartz, 1940; Hill et al. (2017) |
| 1930 | Muscle larva antigen enables T. spiralis diagnosis in pigs. | Schwartz et al. (1930) |
| 1935, 1936 | Elevated (> 4 times) prevalence in in garbage-fed (vs. grain-fed) pigs. | Hall (1937); Schwartz (1940) |
| 1949–1970 | Trichinella prevalence in Arctic and Alaska, USA documented. | Rausch (1970) |
| 1952 | Feeding uncooked garbage to pigs outlawed to control the viral disease vesicular exanthema, reducing prevalence of Trichinella in pigs. | Jefferies et al. (1966) |
| 1958–1972 | International Commission on trichinellosis established. | Dupouy-Camet et al. (2020); Supplementary file 2 |
| 1961 | Benzimidazole treatment introduced as a drug against trichinellosis. | Campbell and Denham (1983) |
| 1967 | Pooled muscle digestion procedure proposed for detection of Trichinella for surveillance. | Zimmermann (1967); Gamble, 1996, Gamble, 1998, Gamble, 1999 |
| 1961–1966 | National survey of Trichinella in pigs by peptic digestion of diaphragms of 43,868 revealed low prevalence in farm-raised pigs. Trichinella infections in pigs and humans in the USA reviewed. | Zimmermann and Brandly (1965); Zimmermann (1970); Zimmermann and Zinter (1971) |
| 1969 | First commercial slaughterhouse testing of Trichinella in pork at a plant in Iowa. Based on 5–8 g samples of diaphragm from each pig tested 42 (0.008%) of 482,392 pigs during a 32-weeks period were positive for Trichinella larvae. The cost of testing was estimated to be 0.1$ per pig. | Andrews et al. (1969) |
| 1972 | Multiple species within the genus Trichinella proposed. Trichinella nelsoni and T. nativa recognized (species characteristics and biology of each species currently recognized are summarized in Table 2. | Britov and Boev (1972); see Table 2 for other authors contributions |
| 1974 | First ELISA test developed for serological diagnosis in pigs. | Ruitenberg et al. (1974); van Knapen et al. (1976) |
| 1980 | Outbreaks of clinical trichinellosis derived from consumption of horse meat recognized in Europe. Experimental demonstration that Trichinella from human is infective to horses. | Mantovani et al. (1980); Ancelle (1998); Soule et al. (1989) |
| 1983, 1988 | A sensitive and specific enzyme-linked immunoassay using excretory-secretory products from T. spiralis larvae developed for the detection of Trichinella antibodies. | Gamble et al., 1983, Gamble et al., 1988,Gamble (1996) |
| 1986 | Cannibalism, not rodents, demonstrated as a major source of infection in an endemic herd of 1000 pigs. | Hanbury et al. (1986) |
| 1987–2006 | Morphology, isoenzymes, geography, and genetics discriminate species of Trichinella. | (see Table 2) |
| 1988 | Establishment of the International Trichinella Reference Centre. | Dupouy-Camet et al. (2020); Marucci et al. (2022); Supplementary file 2 |
| 1996,2007 | Viable T. spiralis can persist in muscles of experimentally infected horses for >12 months in the absence of detectable level of antibodies. 5 g samples of horsemeat found necessary to detect viable Trichinella infections. | Gamble et al. (1996); Hill et al., 2007a, Hill et al., 2007b |
| 1999 | Freeze resistance of Trichinella nativa established. | Kapel et al. (1999); additional details in Pozio, 2016, Pozio, 2020, Pozio, 2022 |
|
1999- 2001 |
Development of Multiplex PCR to diagnose all genotypes of Trichinella that became the international standard for genotyping. | Zarlenga et al., 1999, Zarlenga et al., 2001 |
| 2005 | A USDA, pork industry initiative of Trichinella certification program for pork issued in USA. All 11,713 pigs tested from certified farms tested negative for Trichinella. | Pyburn et al. (2005) |
| 2006 | Evolutionary and biogeographic hypothesis for Trichinellae. | Zarlenga et al. (2006) |
| 2007 | Joint publication of FAO/OIE/WHO Guidelines for the for the surveillance, management, prevention, and control of trichinellosis. | Dupouy-Camet and Murrell (2007) |
| 2008 | Documentation of especially inbred T. spiralis in Europe and the Americas, impairing outbreak tracing. | Rosenthal et al. (2008) |
| 2011 | First draft sequence of any Trichinella genome, revealing marked differences from the C. elegans “model nematode.” | Mitreva et al. (2011) |
| 2015 | Natural introgression among T. spiralis and T. britovi. | Franssen et al. (2015) |
| 2016 | Draft genomes of all known species of Trichinella. | Korhonen et al. (2016) |
| 2017 | First chromosomal assembly of a Trichinella genome. | Thompson et al. (2017) |
| 2018 | Microsatellite markers readily trace transmission of T. britovibut less readily trace transmission of T. spiralis in Europe. | La Rosa et al., 2012, La Rosa et al., 2018; Bilska-Zając et al., 2022 |
| 2022 | Demonstration that genome variation can trace T. spiralis outbreaks. | Rosenthal et al. (2021); Bilska-Zając et al. (2022) |
| 2024 | Testing over 3 million PQA+ pigs via artificial digestion revealed none infected with Trichinella, establishing this production compartment as one of “negligible risk.” | Gamble et al. (2024); see text |