A federal lawsuit in New Jersey alleging an infant was sickened by salmonella-contaminated dog food may be the first in the nation to hit the courts in the wake of a recent pet food recall.

At least 15 people in nine states and Canada have reportedly fallen ill as a result of contact with pet food made by Diamond Pet Foods, which announced the recall on April 6 and has since expanded it to additional brands.

Eisenberg v. Diamond Pet Food Processors, 12-cv- 3127, filed May 25 in federal court in Trenton, alleges that a two-month-old child became sick with diarrhea, fever and loss of appetite on April 11. A day later, his pediatrician sent him to St. Peter’s University Hospital, where he spent three days and was diagnosed with salmonella. A stool sample later tested positive for the same strain of salmonella that spurred the recall, salmonella infantis.

The child’s father, Nevin Eisenberg of Marlboro, alleges he bought a bag of a Diamond brand — Kirkland Signature Super Premium Healthy Weight Dog Food with chicken and vegetables — at the Costco Wholesale Corporation store in Morganville.

The complaint does not specify how the child, identified as C.A.E., became exposed to salmonella.

Eisenberg’s lawyer, Elliot Olsen of PritzkerOlsen in Minneapolis, says the route of transmission to the child is uncertain but there had to have been “some common contact with the dog food and source of food for the kid” and it “might have happened through the parents’ hands.”

The recall notices say people can become infected with salmonella by handling contaminated food “especially if they have not thoroughly washed their hands after having contact with surfaces exposed to this product.”

The Eisenberg family’s dogs did not get sick, nor did the parents, and salmonella was not detected in the bag of dog food, which the Monmouth County Health Department sent to a state health lab for testing after C.A.E. became sick.

Olsen says he is not aware of any other case filed over the recalled foods and PACER records show no federal lawsuit of any kind against Diamond since 2011, before the salmonella problem came to light.

Olsen points out that the salmonella strain contracted by C.A.E. is uncommon and the same as the one that sparked the recall. “To have a child come up with this exact form of salmonella, which is relatively rare, it’s epidemiologically pretty solid,” he says.

Olsen further notes that salmonella contamination would not be spread uniformly throughout the bag of food, which would explain the negative test result.

Though C.A.E. has recovered, he allegedly suffered “severe injuries to his gastrointestinal tract.” He is at risk of kidney and liver damage and monitoring will be needed, Olsen adds.

The seven-count complaint against both Diamond and Costco asserts claims under New Jersey’s Consumer Fraud Act and Product Liability Act, as well as common-law claims like negligence, breach of warranty and fraudulent misrepresentation.

Neither Diamond, based in Meta, Mo., nor Costco, based in Issaquah, Wash., responded to a request for comment about the suit, which has been assigned to U.S. District Judge Joel Pisano and U.S. Magistrate Judge Lois Goodman.

Olsen says his firm came to represent the New Jersey plaintiffs because “we do this kind of work nationwide and have an Internet presence.” The firm’s website boasts a $6.425 million settlement on behalf of three sets of plaintiffs in a food-borne illness matter.

Olsen says that case involved a 2002 outbreak of listeriosis in New York, New Jersey and Pennsylvania that was settled in 2006. He declines to name the parties, but according to the Centers for Disease Control, Pilgrim’s Pride Foods in 2002 recalled 27.4 million pounds of ready-to-eat turkey and chicken products from a plant in Franconia, Pa., that was found to be contaminated with listeria.

Bernard Daskal of Lynch, Daskal & Emery in New York is the plaintiffs’ local counsel.

The pet food recall, which initially involved only Diamond Naturals dog foods, now encompasses a variety of other brands, including cat food, produced between Dec. 9, 2011, and April 7, 2012. Other affected brands include Country Value, Premium Edge, Canidae and Chicken Soup for the Pet Lover’s Soul, as well as Kirkland.

They were manufactured at the Gaston, S.C., facility and distributed in 16 eastern and southern states, including New Jersey, New York, Pennsylvania, Massachusetts and Virginia, and in five Canadian provinces, including Ontario and Quebec.

The contamination came to light April 2 as the result of routine testing by Michigan state authorities on a bag of Diamond Naturals Lamb Meal & Rice dry dog food.

After detecting salmonella infantis, state authorities tracked down people sick from that strain and questioned them, uncovering the common thread of contact with dog food from the Gaston plant, where a Food and Drug Administration inspection found unsanitary conditions.

The states most affected were Pennsylvania, Missouri and North Carolina, which each had three residents with salmonellosis. No one has died but four are known to have been hospitalized in addition to C.A.E.

The CDC recommends checking bags of the affected foods and, if they have the specified production codes, discontinuing use and disposing of them in a closed plastic bag placed in a sealed trash can.