Leptospirosis outbreaks tough to diagnose

Disease may be caused by proximity to wildlife



Introduction

Canine outbreaks of leptospirosis in several states are sparking discussion and controversy about vaccination practices for prevention of the disease and concern for transfer of the disease to humans.

Leptospirosis is a bacterial infection cause by a family of organisms known as Leptospira interrogans. Until recently, vaccines were available for only two strains (Leptospirosis canicola and L. icterhaemorrhagiae), but vaccines for two additional types (L. grippotyphosa and L. pomona) are now on the market. Controversy arises because some dogs are allergic to the carrier in the lepto vaccine; as a result, some veterinarians no longer use the inoculant in areas where the disease is not a problem.

Concern about side-effects are relatively new; clinical canine leptospirosis caused by L. canicola and L. icterhaemorrhagiae is rare in the US, a situation attributed to widespread administration of the vaccine. The new outbreaks are being caused by L. grippotyphosa and L. pomona, strains that are prevalent in some species of wildlife. The theory is that the disease has entered suburban areas with populations of skunks, raccoons, opossums, deer, and small rodents and that dogs become vectors of these strains through contact with the urine of these animals. Lepto can infect livestock as well, so cattle and hogs that wade or wallow in areas contaminated by the urine of carrier animals can also get the disease.

Transmission

Leptospirosis is contracted primarily through contact with the urine of an infected animal, but can also be transmitted through bite wounds and the ingestion of infected material. People at greatest risk of getting the disease are those who regularly clean up after animals (farmers, kennel owners, veterinarians, wildlife rehabilitators, etc.) and those who swim, wade in, or drink contaminated waters. Since dogs constantly sniff the urine spots of other dogs (and wild animals), they are at greater risk than humans.

Leptospirosis is a disease of tropical and temperate climates, so much of the US is susceptible to potential outbreaks. So far, the states of Florida, Alabama, Georgia, Massachusetts, Michigan, New Jersey, and New York have experienced lepto eruptions and cases have surfaced in many other states as well.

Symptoms,diagnosis, treatment

Leptospirosis bacteria multiply rapidly after entering the body. Signs of the disease can begin as soon as two days after exposure or as long as 26 days after contact with infected urine, but generally occur within one-to-two weeks.

“The severity of the disease can vary widely but it has the potential to be extremely severe, and in fact fatal,” wrote Henry Boer DVM of Pioneer Valley Veterinary Hospital in western Massachusetts. “Symptoms are typical of kidney and liver disease, and can include, fever, loss of appetite, muscle pain, dehydration, vomiting, diarrhea and bleeding. Some dogs will have an increased water consumption and urine output while others may have a decreasing output of urine. Jaundice may occur, and the dog may be painful in the abdominal area or in the lower back. In extremely acute cases, a dog may suddenly go into shock and succumb.”

Toss in fatigue, depression, gastrointestinal upset, difficulty breathing, the potential for meningitis and eye inflammation, and a picture of a diagnostic nightmare emerges. To further complicate matters, veterinarians are unlikely to suspect lepto in the early stages of the disease because the symptoms are variable and lepto caused by previously implicated strains has gone off the screen as a threat in most of the nation. Initial suspicions are often aroused by blood tests that show liver or kidney involvement, and the disease is confirmed by finding the bacteria in a urine sample or in a liver or kidney biopsy.

Once diagnosed, lepto can be treated with common antibiotics such as penicillin, tetracycline, and erythromycin. In advanced cases, therapies to deal with any liver or kidney involvement will also be necessary.

A dog that has recovered from disease caused by one strain of leptospirosis will be protected from disease caused by that strain in the future, but that protection does not cross species. Therefore, the dog will remain susceptible to other forms of the disease. Vaccines to protect against the disease must attack each specific strain in order to be effective. To confuse matters even more, vaccinated dogs can have mild cases of the disease that show few or no symptoms and can shed the bacteria in their urine, thus spreading the infectious agent.

Leptospirosis vaccines may only protect dogs for six-to-eight months, so veterinarians in high risk areas recommend twice-yearly vaccination. Each dog owner should work with his pet’s veterinarian to determine whether the risk of lepto outweighs the risk of reaction to the vaccination and whether the potential for outbreaks of L. grippotyphosa and L. pomona are of enough concern to vaccinate against them as well.

Because of the potential for the disease to cause serious illness in humans and because dog owners want their pets protected, canine and human health professionals are increasing their awareness of the disease, their procedures for prevention, and their protocols for diagnosis and treatment. Medical advances are announced every day, so ask your veterinarian for the latest information about lepto to determine the benefits and risks of vaccination for each pet.

Sources

1. Dr. Joe Bodwes DVM, Drs. Foster and Smith Inc. Veterinary Services Department

2. Carole Bolin, DVM, PhD Research Leader National Leptospirosis Reference Center USDA, Agricultural Research Service National Animal Disease Center Ames, IA 50010; cbolin@nadc.ars.usda.gov; cbolin@nadc.ars.usda.govv

3. US Centers for Disease Control and Prevention, National Center for Infectious Diseases, Division of Bacterial and Mycotic Diseases

4. Dr. Henry De Boer Jr.; Working K-9 Veterinary Consultation Service, 738 East Mountain Road, Guilford VT 05301; info@workingk-9vet.com info@workingk-9vet.com

Norma Bennett Woolf

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