Vectors and the diseases they transmit

VECTORS AND THE DISEASES THEY TRANSMIT

Fleas, ticks and mosquitoes can be more than just a nuisance. These organisms, in fact, can also be the main carriers of many of the serious diseases that can affect both humans and our beloved dogs.

Known as “vector-borne diseases,” pathogens or disease-causing organisms spread from one animal host to another by these pesky organisms that act as carriers. They can transmit the disease whenever they bite and feed on a host, such as a dog or even a human.

As you become more careful about protecting your furry friends from these parasites, it’s helpful to know that you’re also reducing the risks associated with vector-borne diseases.

mosquitoes

Female mosquitoes bite and feed on blood. They need proteins in the blood to generate eggs. When a mosquito bites, it not only feeds on blood, but also secretes saliva, which enters the bloodstream.

If the mosquito feeds on an infected animal or human, it can further transmit the infection to other beings, as mosquitoes feed multiple times, from different sources.

The increase in the mosquito population has increased the spread of diseases transmitted through them. These diseases can now be found throughout the world, not just in areas that were once considered high risk for mosquitoes, such as tropical and subtropical regions.

Heartworm disease is a potentially fatal disease that begins when a mosquito infested with the parasite’s larvae bites a dog. The young parasites enter the dog’s body through the wound produced by the mosquito bite and begin the development cycle.

In dogs, these worm larvae develop into adult worms in the heart and surrounding blood vessels, possibly causing heart and lung failure. Mature heartworms reproduce, and new infective stages of the worm, called microfilaria, enter the bloodstream, ready to infect another mosquito as it feeds. This infestation is rarely transmitted from mosquitoes to humans.

A parasitic worm, transmitted by mosquitoes, D. rep it lives in the subcutaneous tissue of the dog, unlike heartworm. Most infestations in dogs are asymptomatic, although your pet may experience skin irritation and swelling, as well as conjunctivitis.

Humans are also susceptible to D. rep also through mosquito bites, but it is believed that most pest larvae introduced into humans die before reaching maturity. Symptoms in humans tend to be localized swelling in most cases.

Ticks hatch from an egg, then go through three life stages, and must feed on blood at each stage to survive. Most ticks feed on all mammals (some even birds, reptiles or even amphibians!) and many ticks need to find a new host for each life stage.

As with mosquitoes, tick saliva enters the host’s body at the site where it feeds. In this way the pathogen is ingested by the tick and possibly transmitted to other host animals.

When a tick feeds, it can remain attached for several days while continuing to feed. The tick does not transmit the disease as soon as it attaches, it takes some time, although the duration can be different for different pathogens.

This is important because treatments that eliminate ticks when they feed on dogs must work quickly enough to prevent transmission of any disease to that dog.

There has been a major increase in the population and movements of tick species. The brown dog tick, for example, was once found mainly in warmer areas of the Mediterranean, but in recent years it has moved further north into Europe. This tick can also be found inside buildings and can survive the colder months by being protected from the winter cold.

Another recent example is the discovery of the Asian cattle tick in the United States in 2017. This tick was previously found in East Asia, where it poses a serious threat. It was recently discovered in New Jersey in a sheep with no history of travel out of the country.

Rapid geographic spread then followed, with animals identified in over ten different states. The movement of this tick is supported by its ability to reproduce through parthenogenesis, a rare form of asexual reproduction in which female ticks can produce offspring without the presence of male ticks.

The Asian cattle tick also infests dogs and can be a vector that spreads Babesia in dogs and, fortunately, does not appear to transmit Lyme disease.

The Asian cattle tick may have entered the United States unnoticed during shipments while feeding on the external ear canals of dogs. Its specific reproductive capacity means that just one female tick entering the country is enough to start a population.

Also called BoreliaLyme disease is caused by a bacterium called Borrelia burgdorferi. This disease is currently the most common disease that can occur in humans and is transmitted through ticks, especially Ixodes ticks.

Dogs can also become infected and develop clinical disease. Diagnosis of Lyme disease remains a challenge in dogs, as it is in humans, and canine Lyme disease is more widely recognized in the United States than in Europe.

Tick ​​bites can expose dogs and humans to a multitude of tiny bacteria that belong to a group called Rickets. These include organisms that cause a variety of diseases:

• Ehrlichiosis
• Anaplasmosis
• Rocky Mountain Spotted Fever – and more

THE SAND FLYES

Sandflies are small midges that grow in moist, dark areas with plenty of available organic matter for their larvae to feed on. Female sandflies need to feed on blood to produce their eggs.

LEISHMANIOZA

Leishmaniasis is a parasitic disease widespread in tropical, subtropical and southern European areas. It is a vector-borne disease, serious and common among dogs in some geographic regions, caused by the protozoan parasite Leishmania of newborns and transmitted by several types of flies.

• It is present in the Mediterranean basin, the Middle East, Central Asia, Central and South America.
• It also occurs in humans and, in the past, the disease in humans manifested itself mainly in children (hence the name children).

• Vaccines are available to help protect dogs from this disease and reduce the need for treatment.

Leishmaniasis spreads to new areas, mainly due to the movement of dogs. For example, 12% of dogs that traveled or moved from infested areas in Germany were positive for the virus. Leishmania of newborns. In the UK, almost 15% of imported dogs test positive for Leishmania.

Infested dogs may increase the risk of leishmaniasis in humans, but the disease is not transmitted directly from dogs to humans. Rather, infested dogs infest even greater numbers of sandflies, which can subsequently lead to the flies biting humans and further spreading the disease.

Unfortunately, this information has led to reduced activity in dog populations in some countries as part of a government policy aimed at controlling the risk to humans. The culling of dogs, whether healthy or sick, is not considered an effective measure to control possible infestations.

Other preventative measures, particularly the use of long-acting treatments that prevent flies from feeding on dogs, in combination with canine vaccinations, are much more effective.

EVALUATION OF VECTOR-BORNE DISEASES

Testing for vector-borne diseases is more common in veterinary clinics in the United States than in Europe.

There is still much to learn about how long after infestation a dog will test positive for the disease; the types of clinical signs an infested dog will develop; when clinical signs are expected; and why some dogs never show clinical signs of infestation.

Furthermore, some dogs may continue to be positive for many years after being infected, as is observed, for example, in the case of infection ehrlichiosisand this fact complicates the interpretation of a positive test as a recent change or as an infestation that occurred in the past.

As a pet owner, your best protection is to be consistent with preventative treatments and schedule regular veterinary visits. If you notice any changes in your dog’s health, bring it to your vet’s attention.