Tick-Borne Diseases
TICK-BORNE DISEASES POSE GROWING CONCERN FOR
PRACTITIONERS
Published in Veterinary Practice News, March 2003
Ticks are a common complaint in most veterinary practices and
it’s easy to view the tenacious little suckers as a minor medical
issue compared to many others. However, experts warn that
underestimating the potential dangers posed by these ancient,
eight-legged parasites can put your patients – and their owners
– at risk of serious, even life-threatening disease.
Hard numbers are difficult to come by, but anecdotal evidence
suggests that the incidence of tick-borne disease is on the rise
in the United States, particularly in regions traditionally known
for their high rates of seasonal infestation. That in itself should
give practitioners pause, but of greater concern among some
researchers is the increasing risk of infection by multiple
organisms.
“Veterinarians should be aware that ticks aren’t limited to
carrying one disease,” confirmed Anthony Carr, DVM, an
associate professor at the Western College of Veterinary
Medicine in Saskatoon, Saskatchewan, Canada. “Ticks often
contain multiple pathogens, so a negative test for one organism
does not rule out tick-borne illness.”
If there’s any doubt at all, veterinarians who suspect a tick-
borne disease should test for the presence of more than one
infectious agent, added Edward Breitschwerdt, DVM, co-director
of the Vector-Borne Disease Diagnostic Lab at North Carolina
State University College of Veterinary Medicine and adjunct
associate professor of medicine at Duke University Medical
Center. “We have detected through polymerase chain reaction
testing the DNA of up to six different organisms in a single dog’s
blood sample,” Dr. Breitschwerdt said. Regional Prevalence
Prevalence of specific diseases depends on where you live
because most tick-borne ailments still tend to be relatively
regional, observed T. Mark Neer, DVM, professor of medicine
and Section Head, Small Animal Medicine, VTH&C at Louisiana
State University. Rocky Mountain Spotted Fever, for example, is
most commonly found in the Central and Southeastern United
States, while Lyme disease remains primarily limited to the
Northeast and some Western regions. As a result, practitioners
in one state may see a high incidence of a particular tick-
transmitted infectious disease while colleagues one state over
may see very little.
Whatever the disease, quick and accurate diagnosis is vital
because such ailments can result in very serious health
problems.
“Most of these diseases are multisystemic in their effects on the
patient. Therefore, just one set of consistent clinical signs is not
very likely from case to case,” Dr. Neer said. “These diseases
cause a wide variety of clinical and clinicopathological
abnormalities that include polyarthropathy, polymyosistis,
neurological signs, anorexia, severe anemia, thrombocytopenia,
epistaxis, endocarditis, anterior uveitis, retinal hemorrhage,
meningitis, petechiations, leucocytosis and
glomerulonephropathy.”
Public Health Concern
Tick-borne infectious disease is more than just a veterinary
concern – it’s also a public health issue because many
organisms that infect small animals can also infect their owners.
As a result, a higher-than-normal incidence of disease among
dogs can be a warning to people who frequent common tick
habitats such as public parks and wilderness areas.
“Pets often act as a kind of sentinel system regarding tick-
borne illness, and that has made the veterinarian’s role far
more important,” Dr. Breitschwerdt explained. “Practitioners
must get in the habit of telling clients, ‘Your dog has this
disease and you and your family must be very careful in regard
to ticks.’ The prompt discovery and removal of ticks is very
helpful in preventing many diseases because ticks must be
attached for a specific period before they can transmit an
organism.”
The adage “an ounce of prevention is worth a pound of cure” is
especially appropriate when it comes to tick-transmitted
infectious diseases. As the risk of infection from multiple
organisms becomes better defined, so does the risk of chronic
illness. Studies have shown, for example, that dogs can be
infected with Ehrlichia for five to seven years before developing
signs of disease. And in humans, some patients who failed to
recover completely from Lyme disease were later found to also
be infected with Babesia. These patients felt better while on
antibiotics, but became chronically fatigued when the antibiotics
were stopped.
“The Lyme disease epidemic put some research money back
into the study of tick-transmitted infectious diseases, mostly in
human medicine but also in veterinary medicine,” Dr.
Breitschwerdt noted. “From this research we found that many of
the ticks transmitting Lyme disease are also transmitting
Babesia and various forms of Ehrlichia – something we knew
about in veterinary medicine many years before the same
organisms were found to be a cause of human infection.
“If we go back, it’s fair to say that the importance of tick-
transmitted infections was greatly underrated and under
recognized 10 or 15 years ago. Here in North Carolina, for
example, the only disease anyone would have talked about at
that point would have been Rocky Mountain Spotted Fever,
whereas now there’s quite a few other diseases that are
routinely recognized by physicians and veterinarians, most of
which have always been here. What’s improved is our ability to
diagnose them.” Promising New Protocols
Also promising are advances in the prevention and treatment
of tick-borne infectious diseases, which have been the subject
of much research in recent years.
At the NCSU Vector-Borne Disease Diagnostic Lab, for
example, Dr. Breitschwerdt and colleagues are studying the
efficacy of combination drug therapy in the treatment of certain
tick-transmitted protozoa such as Babesia gibsonii.
“There is also tremendous interest around the world regarding
vaccines that would prevent transmission of many or all
infectious agents transmitted by ticks,” Dr. Breitschwerdt added.
“Most researchers have come to the conclusion that having a
vaccine for each organism that a tick can transmit is probably
impractical. What would be better is a vaccine that would block
transmission of all agents – essentially an anti-tick vaccine.
“In addition, a number of research labs around the world are
trying to better understand the immune system’s response to
tick attachment . These researchers are looking for specific
mechanisms by which a tick could be killed by the host after
attachment so that the tick doesn’t transmit organisms. It’s very
exciting research, but we should be conservative in our
expectations.”
Though several highly effective tick-prevention products have
been introduced in recent years, practitioners should still
remain knowledgeable about the tick-transmitted infectious
diseases most common to their regions and strive to educate
clients regarding risk prior to the spring and fall tick seasons.
“Animal owners should start applying monthly tick-prevention
compounds about a month before the season starts, just in
case ticks arrive early,” advised Doug Carithers, DVM, Senior
Director of Veterinary Professional Services, Merial Companion
Animal Group. “Dogs should also be appropriately vaccinated
for Lyme disease if they live in an endemic area, and pet
owners should reduce opportunities for moist nesting areas by
cleaning up debris in their yards.”
SIDEBAR: REGIONAL RISKS
The following is a list of tick-borne diseases recognized in the
United States and their general geographic distributions:
E. chaffeensis – Central, Southeastern U.S.
E. risticii – Somewhat nationwide but predominantly
Western U.S.
E. platys – Nationwide but more Southern U.S.
E. ewingii – Upper Midwest, Central, Northeastern U.S.
E. equi (phagocytophila) – Upper Midwest, West,
Northeastern U.S.
(Information courtesy of T. Mark Neer, DVM)
SIDEBAR: KNOW YOUR TICKS
The United States is home to a wide variety of ticks. Following
are those of greatest importance to veterinarians and the
diseases they can transmit:
(Information courtesy of T. Mark Neer, DVM)
SIDEBAR: MERIAL LAUNCHES ‘BE A HEART GUARDIAN’
CAMPAIGN
Merial, in conjunction with the American Animal Hospital
Association and other animal health organizations, has
designated April as National Heartworm Awareness Month, and
is asking all pet owners and veterinarians to “Be A Heart
Guardian.”
As part of this national awareness effort, Merial will launch a
nationwide consumer campaign regarding heartworm
prevention, with special emphasis on the veterinarian’s role in
keeping pets and families safe from zoonotic diseases.
Veterinarians will receive a special media kit with press
releases that can be customized so that practitioners can send
information to their regional media. The “Be A Heart Guardian”
kit also contains counter cards, posters, balloons, heartworm
incidence maps for each county/state, floor clings and window
clings.
“This campaign is geared toward reaching pet owners with
important heartworm information and to encourage them to visit
their veterinarians for proper understanding, treatment and
preventative measures,” said Merial spokeswoman Cindy
Greeno. “It actively showcases Merial’s commitment to adding
real value to our veterinary customers in support of the
important work they do and their role in keeping pets healthy.”
For further information on the “Be A Heart Guardian”
campaign, call Merial at 888-637-4251.
PRACTITIONERS
Published in Veterinary Practice News, March 2003
Ticks are a common complaint in most veterinary practices and
it’s easy to view the tenacious little suckers as a minor medical
issue compared to many others. However, experts warn that
underestimating the potential dangers posed by these ancient,
eight-legged parasites can put your patients – and their owners
– at risk of serious, even life-threatening disease.
Hard numbers are difficult to come by, but anecdotal evidence
suggests that the incidence of tick-borne disease is on the rise
in the United States, particularly in regions traditionally known
for their high rates of seasonal infestation. That in itself should
give practitioners pause, but of greater concern among some
researchers is the increasing risk of infection by multiple
organisms.
“Veterinarians should be aware that ticks aren’t limited to
carrying one disease,” confirmed Anthony Carr, DVM, an
associate professor at the Western College of Veterinary
Medicine in Saskatoon, Saskatchewan, Canada. “Ticks often
contain multiple pathogens, so a negative test for one organism
does not rule out tick-borne illness.”
If there’s any doubt at all, veterinarians who suspect a tick-
borne disease should test for the presence of more than one
infectious agent, added Edward Breitschwerdt, DVM, co-director
of the Vector-Borne Disease Diagnostic Lab at North Carolina
State University College of Veterinary Medicine and adjunct
associate professor of medicine at Duke University Medical
Center. “We have detected through polymerase chain reaction
testing the DNA of up to six different organisms in a single dog’s
blood sample,” Dr. Breitschwerdt said. Regional Prevalence
Prevalence of specific diseases depends on where you live
because most tick-borne ailments still tend to be relatively
regional, observed T. Mark Neer, DVM, professor of medicine
and Section Head, Small Animal Medicine, VTH&C at Louisiana
State University. Rocky Mountain Spotted Fever, for example, is
most commonly found in the Central and Southeastern United
States, while Lyme disease remains primarily limited to the
Northeast and some Western regions. As a result, practitioners
in one state may see a high incidence of a particular tick-
transmitted infectious disease while colleagues one state over
may see very little.
Whatever the disease, quick and accurate diagnosis is vital
because such ailments can result in very serious health
problems.
“Most of these diseases are multisystemic in their effects on the
patient. Therefore, just one set of consistent clinical signs is not
very likely from case to case,” Dr. Neer said. “These diseases
cause a wide variety of clinical and clinicopathological
abnormalities that include polyarthropathy, polymyosistis,
neurological signs, anorexia, severe anemia, thrombocytopenia,
epistaxis, endocarditis, anterior uveitis, retinal hemorrhage,
meningitis, petechiations, leucocytosis and
glomerulonephropathy.”
Public Health Concern
Tick-borne infectious disease is more than just a veterinary
concern – it’s also a public health issue because many
organisms that infect small animals can also infect their owners.
As a result, a higher-than-normal incidence of disease among
dogs can be a warning to people who frequent common tick
habitats such as public parks and wilderness areas.
“Pets often act as a kind of sentinel system regarding tick-
borne illness, and that has made the veterinarian’s role far
more important,” Dr. Breitschwerdt explained. “Practitioners
must get in the habit of telling clients, ‘Your dog has this
disease and you and your family must be very careful in regard
to ticks.’ The prompt discovery and removal of ticks is very
helpful in preventing many diseases because ticks must be
attached for a specific period before they can transmit an
organism.”
The adage “an ounce of prevention is worth a pound of cure” is
especially appropriate when it comes to tick-transmitted
infectious diseases. As the risk of infection from multiple
organisms becomes better defined, so does the risk of chronic
illness. Studies have shown, for example, that dogs can be
infected with Ehrlichia for five to seven years before developing
signs of disease. And in humans, some patients who failed to
recover completely from Lyme disease were later found to also
be infected with Babesia. These patients felt better while on
antibiotics, but became chronically fatigued when the antibiotics
were stopped.
“The Lyme disease epidemic put some research money back
into the study of tick-transmitted infectious diseases, mostly in
human medicine but also in veterinary medicine,” Dr.
Breitschwerdt noted. “From this research we found that many of
the ticks transmitting Lyme disease are also transmitting
Babesia and various forms of Ehrlichia – something we knew
about in veterinary medicine many years before the same
organisms were found to be a cause of human infection.
“If we go back, it’s fair to say that the importance of tick-
transmitted infections was greatly underrated and under
recognized 10 or 15 years ago. Here in North Carolina, for
example, the only disease anyone would have talked about at
that point would have been Rocky Mountain Spotted Fever,
whereas now there’s quite a few other diseases that are
routinely recognized by physicians and veterinarians, most of
which have always been here. What’s improved is our ability to
diagnose them.” Promising New Protocols
Also promising are advances in the prevention and treatment
of tick-borne infectious diseases, which have been the subject
of much research in recent years.
At the NCSU Vector-Borne Disease Diagnostic Lab, for
example, Dr. Breitschwerdt and colleagues are studying the
efficacy of combination drug therapy in the treatment of certain
tick-transmitted protozoa such as Babesia gibsonii.
“There is also tremendous interest around the world regarding
vaccines that would prevent transmission of many or all
infectious agents transmitted by ticks,” Dr. Breitschwerdt added.
“Most researchers have come to the conclusion that having a
vaccine for each organism that a tick can transmit is probably
impractical. What would be better is a vaccine that would block
transmission of all agents – essentially an anti-tick vaccine.
“In addition, a number of research labs around the world are
trying to better understand the immune system’s response to
tick attachment . These researchers are looking for specific
mechanisms by which a tick could be killed by the host after
attachment so that the tick doesn’t transmit organisms. It’s very
exciting research, but we should be conservative in our
expectations.”
Though several highly effective tick-prevention products have
been introduced in recent years, practitioners should still
remain knowledgeable about the tick-transmitted infectious
diseases most common to their regions and strive to educate
clients regarding risk prior to the spring and fall tick seasons.
“Animal owners should start applying monthly tick-prevention
compounds about a month before the season starts, just in
case ticks arrive early,” advised Doug Carithers, DVM, Senior
Director of Veterinary Professional Services, Merial Companion
Animal Group. “Dogs should also be appropriately vaccinated
for Lyme disease if they live in an endemic area, and pet
owners should reduce opportunities for moist nesting areas by
cleaning up debris in their yards.”
SIDEBAR: REGIONAL RISKS
The following is a list of tick-borne diseases recognized in the
United States and their general geographic distributions:
- Rocky Mountain spotted fever (RMSF) – Caused by
Rickettsia rickettsii. More distributed in Central and
Southeastern U.S. - Ehrlichiosis – Can be caused by all of these different
species of ehrlichia:
E. chaffeensis – Central, Southeastern U.S.
E. risticii – Somewhat nationwide but predominantly
Western U.S.
E. platys – Nationwide but more Southern U.S.
E. ewingii – Upper Midwest, Central, Northeastern U.S.
E. equi (phagocytophila) – Upper Midwest, West,
Northeastern U.S.
- Hepatozoonosis – Caused by Hepatozoon americanum.
Distributed in Oklahoma, Gulf Coast states, Southeastern
U.S. - Borreliosis (Lyme disease) – Caused by Borrelia
burgdorferi. Primarily limited to the Northeastern part of
the U.S. and somewhat in the Western states. - Babesiosis – Caused by Babesia canis and B. gibsoni.
Distributed nationwide but B. gibsoni may be seen more
in the Southern and Western U.S. - Cytauxzoonosis in cats caused by Cytauxzoon felis. Seen
more in the Central, Midwest and Southern regions. - Bartonella vinsonii (berkhoffii) – Causes bartonellosis in
dogs. Distributed more in the Southeastern region of the
U.S. - Hemobartonellosis – Caused by Hemobartonella canis.
Distributed nationwide but rarely causes clinical disease.
(Information courtesy of T. Mark Neer, DVM)
SIDEBAR: KNOW YOUR TICKS
The United States is home to a wide variety of ticks. Following
are those of greatest importance to veterinarians and the
diseases they can transmit:
- Amblyomma americanum (Lone Star) – RMSF, Borrelia,
Ehrlichia, Babesia - Amblyomma maculatum (Gulf Coast) – Hepatozoonosis
- Dermacentor andersoni (Rocky Mountain wood tick) –
RMSF - Dermacentor veriabilis (American dog tick) – RMSF,
Babesia, Ehrlichia, Cytauxzoonosis - Ixodes scapularis (Northern deer tick) – Borrelia,
Ehrlichia, Babesia - Ixodes pacificus (Western black-legged tick) – Borrelia,
Ehrlichia - Rhipicephalus sanguineus (Brown dog tick) – Ehrlichia,
Babesia, Hemobartonella, Hepatozoon
(Information courtesy of T. Mark Neer, DVM)
SIDEBAR: MERIAL LAUNCHES ‘BE A HEART GUARDIAN’
CAMPAIGN
Merial, in conjunction with the American Animal Hospital
Association and other animal health organizations, has
designated April as National Heartworm Awareness Month, and
is asking all pet owners and veterinarians to “Be A Heart
Guardian.”
As part of this national awareness effort, Merial will launch a
nationwide consumer campaign regarding heartworm
prevention, with special emphasis on the veterinarian’s role in
keeping pets and families safe from zoonotic diseases.
Veterinarians will receive a special media kit with press
releases that can be customized so that practitioners can send
information to their regional media. The “Be A Heart Guardian”
kit also contains counter cards, posters, balloons, heartworm
incidence maps for each county/state, floor clings and window
clings.
“This campaign is geared toward reaching pet owners with
important heartworm information and to encourage them to visit
their veterinarians for proper understanding, treatment and
preventative measures,” said Merial spokeswoman Cindy
Greeno. “It actively showcases Merial’s commitment to adding
real value to our veterinary customers in support of the
important work they do and their role in keeping pets healthy.”
For further information on the “Be A Heart Guardian”
campaign, call Merial at 888-637-4251.