One major fact revealed by a University of Missouri study looking at indoor pork production is that it has improved the pigs’ health and the product for consumers.

According to Missouri’s Extension Commercial Agriculture Swine Focus, since pigs have been moved inside to concentrated- animal-feeding operations and have less access to dirt, veterinarians have seen a significant drop in parasites.

In the 1940s, 55 percent to 70 percent of pigs were infected with lung worms. By the 1970s only 11 percent of farms had outbreaks. “In the past decade, lung worms were rarely seen,” says Beth Young, DVM, with the university’s commercial agriculture program. “Likewise, 78 percent to 94 percent of pigs were infected with kidney worms in the 1940s; now infestations are rarely seen.

“Trichinella was found in at least 0.6 percent of pigs in the 1940s; today its presence is only detected at 0.0007 percent,” Young says. Scientists believe that’s because pigs are not feeding on garbage and have no access to wildlife indoors. The only real danger now of contracting trichinella via meat is from eating game meat.

In the 1970s, toxoplasma was noted in 42 percent of sows, and it’s now down to 6 percent. Cats are the most likely carriers of the parasite. For example, humans have learned to be careful when changing kitty litter and, thereby, have greatly reduced possible infection.

Young points out that many other swine diseases have shown significant decreases or eradication since moving pigs indoors. The list includes swine dysentery, atrophic rhinitis, Actinobacillus pleuropneumoniae, brucellosis, classical swine fever (hog cholera) and pseudorabies.

“Animal-rights organizations are quick to criticize CAFOs,” Young says. “But evidence of the decline or eradication of these diseases cannot be refuted, nor easily attributed to other circumstances.”