Heartworm disease in dogs – Causes. Symptoms. Treatment
Dirofilariasis or heartworm disease is one of the most serious and sometimes fatal diseases affecting dogs. If left untreated, your pet’s life could be in danger. In today’s article, we will discuss the causes of heartworm disease, how the disease progresses, what are the symptoms, treatments and how we can prevent this disease.
What is Dirofilariasis?
Dirofilariasis is a parasitic disease that was first reported in 1847. This condition has become common in many parts of the world and is transmitted by mosquitoes. Most of the time, dogs are affected by heartworm disease.
Heartworm disease – causes
Mosquito bites transmit dirofilariasis. They infect the pet’s body with the parasite Dirofilaria immitis. These parasites are also known as heartworms. When a mosquito bites a dog or cat, the parasite’s larvae are stored under the skin near the bite site. The larvae move from the wound to the bloodstream and reach the heart and pulmonary arteries. This larva can only be seen under a microscope, as it has a size of 30 centimetres in the adult form within seven months. Adult females produce microfilariae that begin to circulate through blood vessels, and these can be swallowed by other mosquitoes and passed on to other dogs or cats.
These parasitic worms can live between 5-7 years in dogs and 2-3 years in cats. Each season with mosquitoes can lead to an increase in the number of worms in protected animals. Microfilariae need mosquitoes to grow into adults. Otherwise, they remain in this chick stage, with a lifespan of 2 years. Thus, the worm needs a mosquito to reproduce. A dog can have up to 300 worms in its body. Females produce millions of microfilariae that live in the small vessels of the bloodstream.
These parasites are called heartworms because, in the case of massive infections, these worms populate the hearts of infected animals.
Dirofilaria immitis is a thin, whitish nematode resembling a violin string. Females are 15-30 cm long and 1-1.5 mm wide. Males are 10-20 cm long and 0.6-0.99 mm wide, with a caudal extremity spiral and provided with five pairs of solid and ovoid papillae. Embryos deposited by females are called microfilariae. They circulate in the blood for almost two years, waiting for the intermediate host.
Types of heartworm disease
There are two types of dirofilariasis:
– Cutaneous heartworm disease is caused by heartworm disease and affects the skin, being contagious to humans.
– Cardiopulmonary heartworm disease: is caused by the parasite Dirofilaria immitis. It is not a danger to humans but can be fatal to dogs, cats and other pets.
Heartworm disease – a symptom
In most cases, dogs are more likely to be infected with the parasitic worm that causes heartworm disease.
In the early stages of the disease, pets show little or no symptoms. When the condition is in an advanced stage, the main signs are:
– Fatigue after the slightest effort
– Syncope – loss of consciousness
– Tachypnea (increased respiratory rate during rest or sleep
– Fibrosis and blood vessel distension
– Pulmonary thrombosis (clots in the lungs) due to blocked blood flow
– Hepatic or renal impairment
The disease is divided into four categories, each with specific symptoms:
– Class 1 – dogs are asymptomatic, which means they have no visible signs of illness or have weak symptoms, such as a rare cough
– Class 2 – dogs show dry cough and intolerance to physical exertion
– Class 3 – the dogs’ physical condition deteriorates – they lose weight, the fur deteriorates, and they lose muscle mass. Breathing difficulties occur, associated with the accumulation of fluid in the abdominal cavity
– Class 4 – dogs in this stage of the disease have no chance of survival, the dog being infected with many heartworms. The parasites block the flow of blood to the heart.
Dirofilariasis – diagnosis
Dirofilariasis can be diagnosed by several tests, as follows:
For diagnosing microfilariae:
– A blood smear
– Knott test
To detect adult worms:
– Test Snap 4Dx
– PCR, Elisa test
– Cardiac ultrasound
– Chest X-rays
Dirofilariasis – treatment
Heartworm disease can be treated with personalized treatments, depending on the stage of the disease. In the first stage, a stabilization treatment is administered, and later the veterinarian intervenes with a drug treatment that kills the parasite. The pet will also be hospitalized when the treatment is applied. Anti-inflammatory and anti-vomiting medications are also given when appropriate.
Dogs with heartworm disease have little chance of survival.
A monthly medication prescribed by a veterinarian may be given to prevent heartworm disease. Before starting, the dog should be tested to see if it is infested with heartworms. All dog breeds are prone to heartworm disease.
Heartworm disease is not transmitted to humans or from an infected dog to a healthy dog. The condition can only be transmitted through the bite of a carrier mosquito. During and after treatment, it is necessary to limit the dog’s physical activity because the worms begin to die, break, and cause blockages in the blood vessels of the lungs, which can lead to the death of the animal.
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