Tick (Ixodes ricinus)
The CDC’s newly released data on Lyme disease, ehrlichiosis, and anaplasmosis underscore the One Health nature of these diseases and the attention required from both human and veterinary health care professionals.
By Amanda Carrozza
The Centers for Disease Control and Prevention (CDC) is warning Americans of the significant diseases related to mosquitoes, fleas, and ticks that may affect people in the United States. Much like the Companion Animal Parasite Council’s (CAPC) forecast, the report’s findings aren’t encouraging—and provide further proof that these vector-borne diseases are a One Health issue.
“Zika, West Nile, Lyme, and chikungunya—a growing list of diseases caused by the bite of an infected mosquito, tick, or flea—have confronted the US in recent years, making a lot of people sick,” said CDC Director Robert Redfield, MD.
As detailed in the CDC’s Vital Signs report this month, 642,602 cases of human illnesses caused by ticks, fleas, or mosquitoes were reported between 2004 and 2016. The agency also noted the presence of 9 types of germs not previously found in the United States.
Of these, 7 were tickborne. Moreover, the rate of reported diseases transmitted through ticks more than doubled over the 13-year period, accounting for more than 60% of all mosquito-, flea-, and tick-associated illnesses.
“Our nation’s first lines of defense are state and local health departments and vector [pathogen carrier] control organizations,” Dr. Redfield noted. “And we must continue to enhance our investment in their ability to fight against these diseases.”
The CDC also reported that the most common tick-transmitted diseases in the United States in 2016 were Lyme disease, ehrlichiosis, and anaplasmosis. These data closely mirror CAPC’s prediction that non-endemic areas will start to see a rise in Lyme disease cases in 2018, including in North Dakota, South Dakota, Iowa, Missouri, southern Illinois, Ohio, Kentucky, Tennessee, North Carolina, western Pennsylvania, eastern Ohio, West Virginia, and the Appalachian region in Virginia.
Additionally, the CAPC warned veterinarians that anaplasmosis prevalence is forecasted to be average for much of the country this year, except for Minnesota, which is expected to see a spike in activity. Ehrlichiosis prevalence is expected to be higher than normal in the southern Virginia and northern North Carolina regions, with normal prevalence elsewhere.
American Veterinarian® also reported on a recent retrospective study conducted by IDEXX researchers that found an association between dogs with positive Lyme disease or Ehrlichia test results and an increased risk for chronic kidney disease. The investigators found that dogs with 1 vector-borne disease had a 300% increased risk of developing kidney disease when Ehrlichia antibodies were present in dogs living in E canis–endemic areas, and a 43% increased risk of developing kidney disease when Borrelia antibodies were present.
This research, coupled with the CDC and CAPC reports, emphasize the importance of preventive compliance and regular screenings for pets.
What are Vector Born Diseases?
Key facts
· Vector-borne diseases account for more than 17% of all infectious diseases, causing more than 700 000 deaths annually.
· More than 3.9 billion people in over 128 countries are at risk of contracting dengue, with 96 million cases estimated per year.
· Malaria causes more than 400 000 deaths every year globally, most of them children under 5 years of age.
· Other diseases such as Chagas disease, leishmaniasis and schistosomiasis affect hundreds of millions of people worldwide.
· Many of these diseases are preventable through informed protective measures.
Main vectors and diseases they transmit
Vectors are living organisms that can transmit infectious diseases between humans or from animals to humans. Many of these vectors are bloodsucking insects, which ingest disease-producing microorganisms during a blood meal from an infected host (human or animal) and later inject it into a new host during their subsequent blood meal.
Mosquitoes are the best known disease vector. Others include ticks, flies, sandflies, fleas, triatomine bugs and some freshwater aquatic snails.
Mosquitoes
· Aedes
· Chikungunya
· Dengue fever
· Lymphatic filariasis
· Rift Valley fever
· Yellow fever
· Zika
· Anopheles
· Malaria
· Lymphatic filariasis
· Culex
· Japanese encephalitis
· Lymphatic filariasis
· West Nile fever
Sandflies
· Leishmaniasis
· Sandfly fever (phelebotomus fever)
Ticks
· Crimean-Congo haemorrhagic fever
· Lyme disease
· Relapsing fever (borreliosis)
· Rickettsial diseases (spotted fever and Q fever)
· Tick-borne encephalitis
· Tularaemia
Triatomine bugs (also known as conenose bugs, kissing bugs, assassin bugs, or vampire bugs)
· Chagas disease (American trypanosomiasis)
Tsetse flies
· Sleeping sickness (African trypanosomiasis)
Fleas
· Plague (transmitted by fleas from rats to humans)
· Rickettsiosis
Black flies
· Onchocerciasis (river blindness)
Aquatic snails
· Schistosomiasis (bilharziasis)
Lice
· Typhus and louse-borne relapsing fever
Vector-borne diseases
Vector-borne diseases are human [and animal] illnesses caused by parasites, viruses and bacteria that are transmitted by mosquitoes, sandflies, triatomine bugs, blackflies, ticks, tsetse flies, mites, snails and lice. Every year there are more than 700 000 deaths from diseases such as malaria, dengue, schistosomiasis, human African trypanosomiasis, leishmaniasis, Chagas disease, yellow fever, Japanese encephalitis and onchocerciasis, globally.
The major vector-borne diseases, together, account for aeround 17% of all infectious diseases. The burden of these diseases is highest in tropical and subtropical areas and they disproportionately affect the poorest populations. Since 2014, major outbreaks of dengue, malaria, chikungunya yellow fever and Zika have afflicted populations, claimed lives and overwhelmed health systems in many countries.
Distribution of vector-borne diseases is determined by complex demographic, environmental and social factors. Global travel and trade, unplanned urbanization and environmental challenges such as climate change can impact on pathogen transmission, making transmission season longer or more intense or causing diseases to emerge in countries where they were previously unknown.
Changes in agricultural practices due to variation in temperature and rainfall can affect the transmission of vector-borne diseases. The growth of urban slums, lacking reliable piped water or adequate solid waste management, can render large populations in towns and cities at risk of viral diseases spread by mosquitoes. Together, such factors influence the reach of vector populations and the transmission patterns of disease-causing pathogens.
WHO response
The Global vector control response (GVCR) 2017–2030 approved by the World Health Assembly (2017) provides strategic guidance to countries and development partners for urgent strengthening of vector control as a fundamental approach to preventing disease and responding to outbreaks. To achieve this a re-alignment of vector control programmes is required, supported by increased technical capacity, improved infrastructure, strengthened monitoring and surveillance systems, and greater community mobilization. Ultimately, this will support implementation of a comprehensive approach to vector control that will enable the achievement of disease-specific national and global goals and contribute to achievement of the Sustainable Development Goals and Universal Health Coverage.
WHO Secretariat provides strategic, normative and technical guidance to countries and development partners for strengthening vector control as a fundamental approach based on GVCR to preventing disease and responding to outbreaks. Specifically WHO responds to vector-borne diseases by:
· providing evidence-based guidance for controlling vectors and protecting people against infection;
· providing technical support to countries so that they can effectively manage cases and outbreaks;
· supporting countries to improve their reporting systems and capture the true burden of the disease;
· providing training (capacity building) on clinical management, diagnosis and vector control with some of its collaborating centres throughout the world; and
· supporting the development and evaluation of new tools, technologies and approaches for vector borne diseases, include vector control and disease management technologies.
A crucial element in vector-borne diseases is behavioural change. WHO works with partners to provide education and improve awareness so that people know how to protect themselves and their communities from mosquitoes, ticks, bugs, flies and other vectors.
For many diseases such as Chagas disease, malaria, schistosomiasis and leishmaniasis, WHO has initiated control programmes using donated or subsidized medicines.
Access to water and sanitation is a very important factor in disease control and elimination. WHO works together with many different government sectors to control these diseases.
