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Vector-borne diseases

DVM InFocus

But ticks move as we move pets, production and wild animals — this is a national and an international issue. We're relocating wild animals throughout the United States, and rescue organizations are bringing in dogs from places like Europe, the Caribbean and Iraq. These organizations usually try to screen as best they can for chronic vector-borne infections, but no testing is 100 percent reliable.

In addition, companion animals while on vacation can pick up ticks and tick-borne infections and take them back home to a completely different area of the country. At times, these vectors can then perpetuate a new transmission cycle in a setting in which veterinarians are less familiar with tick-borne illnesses.

DVM: Are there new mechanisms in place to monitor vector-borne parasitic disease? If so, what are they and how effective are they?

Dr. Breitschwerdt: We used to rely on seroconversion tests with samples obtained at the time of suspected infection, then several weeks later looked for the level of antibodies to go from low to high. But now we have access to DNA-based diagnostic tests that can confirm active infection from tick diseases within a matter of hours.

If the test is positive, that confirms the tick-borne cause of the illness and targeted treatment can be initiated. These molecular diagnostic tests are very useful, but have limitations.

The most effective mechanism to monitor for the prevalence of vector-borne diseases is rapid in-house annual screening using approved products such as the 4Dx assay. Annual screening is important for three reasons: first, it allows veterinarians to screen for evidence of infection prior to the onset of illness; second, any change in prevalence of tick-borne organisms can be detected; and third, veterinarians can play a role in public-health monitoring of vector-borne infectious diseases in their local communities, because most of these organisms infect both dogs and humans.

If practitioners are aware of transmission patterns, they can advise pet owners with regard to daily monitoring for tick attachment to family members — how to carefully and completely remove the tick — and, in case of unexplained febrile illness in family members, to notify the family physician of the presence of infection or exposure of a dog in the same household.

In some areas of the country, veterinarians may be more knowledgeable about tick-transmitted infectious diseases than physicians.

Open communication among veterinarians and physicians is the most important thing when it comes to the management of these vector-borne pathogens. We'll see 50 ticks on a dog before the first tick appears on a human sharing the same environment. If dogs are contracting anaplasmosis, ehrlichiosis or Rocky Mountain Spotted Fever (RMSF), then people in the area may be suffering from these same infections.

For example, clinical manifestations in dogs with RMSF are identical in most instances to manifestations reported in human patients. From a public-health perspective, the dog is an environmental sentinel for RMSF; it is therefore important that veterinarians recognize and accurately diagnose RMSF.

Diagnostic confirmation in a dog using DNA testing or seroconversion allows veterinarians to discuss the risk of R. rickettsii transmission in the peri-domestic surroundings. With appropriate treatment, both dogs and humans show rapid improvement within 24 hours. However, selection of an ineffective antibiotic could lead to death of the dog or the human in the same household.

DVM: Describe the practitioner's role in monitoring vector-transmitted disease. How has this role changed in the last five years?

Dr. Breitschwerdt: Veterinarians monitor for vector-transmitted disease in two ways: by diagnosis of active infections in their patients, and by using annual screenings to determine if dogs have been exposed to organisms, especially those that cause chronic infections and, ultimately, disease.

Veterinarians are being more pro-active in the diagnosis of vector-transmitted diseases, and a major change is the recognition among veterinarians of how important flea- and tick-transmitted pathogens are in daily practice, important from the standpoint of both animal health and human heath.

It is more important now to keep fleas and ticks off dogs and cats than it has ever been in the history of the profession.

Ms. Wetzel is a freelance writer in Cleveland, Ohio.

Disclosure: Dr. Breitschwerdt consults with IDEXX Laboratories and research in his laboratory is funded by a number of pharmaceutical companies that produce acaracide products.


Source: DVM InFocus,
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