Table 3.
Prevalence of Trichinella in domestic pigs tested at USDA laboratories.
| Year tested |
Region⁎ | No. tested | Method | No. positive (%) |
Notes | Reference |
|---|---|---|---|---|---|---|
| 1898-1906 | North central states | 8,257,928 | Trichinoscope (discontinued in 1906) |
212,228 (2.57) | 1.41% contained live and 1.126% dead or degenerated larvae | Ransom (1915); Schwartz (1929) |
| 1936 | 2,341 4,740 |
Digestion Digestion |
130 (5.5) 53 (1.11) |
Garbage fed Grain fed |
Schwartz (1936) | |
| 1933-1937 | 11 states | 6,622 6,484 1987 |
Digestion Digestion Digestion |
60 (0.91) 286 (4.41) 11 (0.55) |
Grain fed Garbage fed Cooked garbage fed |
Schwartz, 1938, Schwartz, 1939 |
| 1935 | 1973 2146 3254 |
Digestion | 95 (4.8) 33 (1.5) 0 |
Garbage fed Grain fed Processed pork products |
Hall, 1935, Hall, 1937 | |
| 1930’s | 13,000 10,500 |
Digestion | 126 (0.95) 599 (5.7) |
Farm-raised, 1-5 larvae/100g Garbage fed |
Schwartz, 1940, Schwartz, 1952 | |
| 1948-1952 | 3,500 | Digestion | 20 (0.57) | 1-5 larvae/100g pork | Schwartz (1960) | |
| 1969 | 1 commercial plant in Fort Dodge, Iowa | 482,392 | Digestion | 42 (0.008%) | The cost of testing was estimated to be 0.1$ per pig (see text). | Andrews et al. (1969) |
| 1971-1975 | Illinois | 50,235 | Digestion | 67 (0.13) | 30,644 herds tested. See text | Hill et al. (1985) |
| 1982-1983 | New England (CT, ME, MA, NH, RI, VT) | 5,315 | Digestion | 39 (0.73) | Infected pigs were from small farms. Prevalence was higher in pigs slaughtered in small custom slaughterhouses versus commercial slaughterhouses | Schad et al. (1985b) |
| 1981-1983 | Mid -Atlantic (PA, NJ, IN, IL, VA, OH, NY, DE) |
33,482 | Digestion | 196 (0.58) | Infected pigs from small backyard pigs in PA, NJ. | Duffy et al. (1985) ; Schad et al. (1985a) |
| 1983 | New Jersey | 63 | Digestion | 56 (88.9) | Poorly managed farm-see text for on farm epidemiology. T spiralis genotyped. Fecundity compared with wildlife T. spiralis isolates |
Schad et al. (1987); Murrell et al. (1987); Leiby et al. (1985) |
| 1984-1988 | Illinois (East St. Louis), poorly managed farm) | 66,854 | Digestion | 0 | See text for epidemiological studies | Doby and Murrell (1989) |
| 1989-1990 | Hawaii | 509 | ELISA | 2 (0.3) | Infected pigs were garbage fed | Dubey et al. (1992) |
| 1990 | NAHMS | 3048 (lactating sows) | ELISA | 5 (0.16) | Sows from 24 states. 5 infected sows were from different herds in NC, OH, PA | USDA-APHIS information sheet (2011); Gamble and Busch (1999) |
| 1995 | NAHMS | 7987 (finishers) | ELISA | 1 (0.013) | 16 states | Gamble and Busch (1999) |
| 1994-1995 | North Carolina | 2183 | ELISA | 1 (0.046) | Infected pig housed outdoors on dirt lot | Davies et al. (1998) |
| 2000 | NAHMS | 14,328 | ELISA | 0 | 17 states | USDA-APHIS information sheet (2018) |
| 2006 | NAHMS | 6238 | ELISA | 0 | 17 states | USDA-APHIS info sheet (2011) |
| Not stated | New England New Jersey |
2132 1946 |
ELISA, digestion ELISA, digestion |
10 (0.47), larvae in 4 of 10 5 9 (0.26) |
Risk assessment study (see text), 90 farms 90 farms |
Gamble et al. (1999) |
| Trichina Certification Project | 11,713 | ELISA, digestion | 0 | 461 farms | Pyburn et al. (2005) | |
| 2007 | Maryland, poorly managed farm | 50 | Digestion | 17 (34.0) | T. spiralis genotyped in all pigs | Hill et al. (2010) |
| 2012 | NAHMS | 5705 | ELISA | 1 | 13 states | USDA-APHIS information sheet (2018) |
| 2024 | Commercial pigs slaughter | >3,000,000 | Digestion | 0 | Risk assessment | Gamble et al. (2024) |
⁎
CT = Connecticut, DE = Delaware, IN=Indiana, IL = Illinois, ME = Maine, MD = Maryland, MA = Massachusetts, NH=New Hampshire, NJ = New Jersey, NY=New York, OH=Ohio, PA = Pennsylvania, RI = Rhode Island, VA = Virginia, VT = Vermont.