Human Illness Associated with Veterinary Vaccines

Abstract & Commentary

Synopsis: Use of veterinary vaccines has decreased disease and illness in animals, but inadvertent human exposure to these vaccines, in particular live vaccines, actually has the potential to cause human infections and illness.

Source: Berkelman RL. Human illness associated with use of veterinary vaccines. Clin Infect Dis. 2003;37:407-414.

The United States Department of Agriculture (USDA) currently licenses more than 2000 vaccines for use in animals. Many of these vaccines are inactivated formulations, but at least 500 are live vaccine formulations, with a potential for inadvertent infections of humans. At highest risk for exposures are veterinarians, animal workers, and pet owners. Reports from the literature as well as personal communications with health officials, veterinary schools, and universities were the basis for this article.


In 1934, the US Brucellosis Eradication Program was begun to eliminate brucellosis in cattle. An early live bacterial vaccine, called S19, was administered for many years and later replaced with a modified live culture vaccine, RB51, in 1996. In unpublished data from the CDC’s passive surveillance registry between 1998 and 1999, 26 individuals reported exposure to RB51 vaccine either via needlestick injury (21 patients), splashes to the eye (4 patients), or a splash to an open wound (1 patient).

Most exposed patients received prophylactic antibiotics (73%), yet a proportion of those so affected still had persistent symptoms for over 6 months (27%). One patient required surgery and Brucella abortus strain RB51 was isolated from the surgical wound.

In other countries, human illness has been reported from accidental exposure to the live vaccine, Brucella melitensis strain Rev-1, which is used worldwide. Two such cases, reported from Spain, were female veterinarians with febrile, systemic illnesses after inadvertent needlestick injuries while vaccinating sheep. Brucellosis was confirmed by serology and culture of the vaccine strain of Brucella melitensis in both cases. Treatment with doxycycline and rifampin resulted in complete recovery.1

Oral Rabies Wildlife Vaccine

Recombinant vaccinia-rabies glycoprotein virus vaccine within oral baits has been used in Europe for 20 years, and in the United States (10 years), to control the spread of rabies in wildlife populations. Humans may have inadvertent exposure to vaccinia virus through contact with these baits. A 26-year-old woman with epidermolytic hyperkeratosis, who was also 15 weeks pregnant, was bitten on the arm by her dog while removing the bait from its mouth. Several days later she developed vesicular lesions with pain, erythema, and swelling of her forearm. The skin lesions progressed to necrotic lesions with axillary adenopathy. Electron microscopy of tissue from the lesions revealed typical orthopoxvirus morphology, and genetic evaluation confirmed the source as vaccinia-rabies glycoprotein virus.2 Toll-free numbers to report exposures are often included on the baits, and simple procedures such as hand washing after any handling of these baits can help prevent exposures.

As the use of these bait vaccines continue to increase, it would seem prudent to ask about possible exposure to such baits in any patient presenting with vesicular lesions.

Bordetella bronchiseptica

Bordetella bronchiseptica is a cause of tracheobronchitis in dogs, atrophic rhinitis in swine, and disease in rabbits and other mammals. Human illness from B bronchiseptica can occur in healthy and immunosuppressed patients ranging from a pertussis-like illness to pneumonia, sepsis, and death.3 Vaccines for "kennel cough" in dogs can contain B bronchiseptica live vaccine and parainfluenza virus for intranasal aerosol administration. In one case, a 14-year-old boy, holding his dog’s head during administration of the intranasal vaccine, was accidentally sprayed directly in the face with the vaccine. The boy later developed a persistent paroxysmal cough with post-tussive vomiting that eventually responded to antibiotic treatment. Although cultures from the patient were not done, the CDC was later able to grow 2 morphologically different colonies of B bronchiseptica representing vaccine of the same lot to which the boy had been exposed (Sanden G. CDC. Unpublished data).

Intranasal administration of live vaccines to animals is convenient, yet it can result in inadvertent exposure to humans, especially if the animals sneeze, which often occurs if liquid is delivered intranasally. For children or adults presenting with a pertussis-like illness, physicians should inquire about exposure to veterinary clinics or recently vaccinated or sick animals.

Comment by Mary-Louise Scully, MD

The topic of animal vaccines and their risk to humans is intriguing and timely, especially as significant numbers of HIV, cancer, and transplant patients may also be pet owners. The licensing and regulation of animal vaccines is under the USDA but is less stringent than the regulation and licensing of human vaccines under the auspices of the FDA. Adverse reactions or illness to animal vaccines can be reported to the Center for Veterinary Biologics, within the USDA’s Animal and Plant Health Inspection Service (APHIS), either by using the toll-free telephone hotline (800-752-6255), or by their web site ( Berkelman’s article is insightful and highlights the need for more careful monitoring, reporting, and possibly better packaging instructions to veterinarians, regarding the ability of live animal vaccines to cause disease in humans.

Animal vaccine production is a large, successful industry in the world market of veterinary animal health. In the United States, Fort Dodge Animal Health (a division of Wyeth Corporation) recorded net sales of $653 million in 2002. Sales in part may reflect the recent license approval for the Fort Dodge Animal Health West Nile Virus vaccine, a killed vaccine product. Despite some concerns that the vaccine may cause pregnant mares to abort or give birth to deformed foals, the APHIS feels the vaccine is safe for horses and strongly recommends its use. In 2002, West Nile virus caused 14,717 equine cases, with another 2168 equine cases so far in 2003. As the veterinary vaccine is a killed vaccine, there is less potential for human illness with accidental exposure. Unfortunately, the time frame for development and subsequent approval of a human vaccine for West Nile virus is not as close at hand.

Vaccination programs for animals have had an overall beneficial effect in reducing disease in domestic and farm animals. In addition, the rabies bait vaccine program has helped arrest the spread of rabies in terrestrial animals in the United States and Europe. However, the lines of communication need to remain open between the government agencies, vaccine manufacturers, veterinarians, and physicians, to ensure adequate exchange of information about the potential effects of these veterinary vaccines on public health.

Dr. Scully, Seattle, WA.


1. Blasco JM, Diaz R. Lancet. 1993;342:805.

2. Rupprecht CE, et al. N Engl J Med. 2001;345:582-586.

3. Dworkin MS, et al. Clin Infect Dis. 1999;28:1095-1099.