Babesiosis
Babesiosis is caused by a protozoan (single-celled) parasite known as a piroplasmid, namely Babesia canis. During its life cycle, this parasite must pass through a vector host before transmitting the disease from one dog to another. The vector is the female tick.
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Parasitic development in dogs has several stages corresponding to changes in the parasite. At first, the parasite is a very simple, circular organism known as a trophozoite. It enters the red blood cells and feeds on their hemoglobin, which it digests. The trophozoite undergoes asexual reproduction (simple cell division). The nucleus of the cell divides first, then the membrane and cytoplasm (the liquid contained within the membrane). The division results in two droplet-shaped daughter cells, or merozoites, which are still inside the red blood cell. There may be more than two cells inside one red blood cell. Usually, the red blood cell is destroyed after division and the merozoites are released into the bloodstream. Each merozoite quickly attaches to another red blood cell, enters it, and forms a trophozoite. Some piroplasmids, called gamonts, stop dividing in the red blood cells.
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Piroplasma developing in erythrocytes
© Bourdeau
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The tick, an intermediate host, takes a meal on an infested dog. The red blood cells it ingests are destroyed in its intestine, as are the trophozoites and merozoites. Only the gamonts remain, which become gametes in the intestinal wall. Two gametes fuse, forming an egg, or zygote. The zygote produces a motile form that leaves the tick's intestine to enter its egg cells, where it multiplies and gives rise to motile spores. If a female tick in the next generation, i.e., one arising from an egg containing motile spores, bites a dog, the motile spores move into her salivary glands. Each motile spore becomes very large, and is then called a sporont. Inside the sporont, thousands of sporozoites form and infest the dog. Each sporozoite enters a red blood cell and becomes a trophozoite to complete the cycle.
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Babesiosis is especially frequent in hot and temperate climates, in areas where ticks are abundant. It is more widespread during seasons in which ticks are active, and with certain lifestyles, as in hunting dogs. Highly-selected breeds such as Cocker Spaniels, spaniels, Yorkshire Terriers, and Dobermans are more susceptible than others. Puppies are more vulnerable than adults.
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The incubation period, which corresponds to the period during which the parasites are multiplying in the dog's body, can last from two days to about two weeks. During this stage, no piroplasmids are present in the blood. After this stage, the parasites appear in the blood and symptoms appear almost simultaneously. In the acute form of this disease, the dog has a very high fever and is exhausted. The fever lasts an average of six to ten days. At the same time, anemia (pallor of the mucosa) is present due to the destruction of red blood cells as the parasites multiply inside of them. After several days of illness, hemoglobinuria arises and blood appears in the urine. Atypical clinical symptoms can be nervous, respiratory, digestive, cutaneous, or visual. The course of the disease is short: one week at the most. The dog becomes worse if untreated and falls into a coma leading to death. There is a chronic form of the disease, found mainly in adults, that can follow an acute form. The fever is not as high, or is absent, and the overall condition of the dog remains good. Anemia is always clearly present. This is a slow form of babesiosis, and complications may occur. The disease may last several weeks and end with the dog's death.
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Diagnosis is made based on the presence of fever and anemia. The dog's lifestyle should be taken into account. Microscopic examination of the blood can confirm the diagnosis. A blood sample is taken from a peripheral area—usually the ear—and examined for the presence of Babesia in the red blood cells. The parasites are more difficult to find in the chronic forms of the disease, since there are fewer in the blood.
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There are treatments specific for Babesia, of which the most frequently-used is imidocarb. Sometimes two injections at an interval of forty-eight hours are necessary, since there is a risk of relapse. In addition to this specific treatment, the symptoms of the disease can be treated, particularly the anemia (by means of antianemic agents, or blood transfusions in the most serious cases).
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Prevention is still the best cure. The disease can be prevented by destroying all ticks as early as possible, and by using acaricide (anti-tick) treatments.
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There is a vaccine for babesiosis, but it is active for a maximum of only six months and is only about seventy percent effective. The protocol for the vaccination consists of two injections three weeks apart, followed by a yearly booster.
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Leishmaniosis
Leishmaniosis is a parasitic disease that primarily affects dogs and is caused by a single-celled parasite (Leishmania infantum) that is transmitted by a vector insect (the female sandfly) which lives mostly on the Mediterranean coast of Europe. This sandfly ingests leishmania from infested dogs and can transmit them to other individuals one to two weeks after ingestion.
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There are several clinical forms of the disease in dogs: Veterinarians working in an infested zone should immediately suspect infestation when a dog presents with an ulcerated lesion on its nose (inoculation chancre) and becomes lethargic and gaunt (marked change in temporal muscles, making the afflicted dog look "old"). Other signs such as pronounced rib cage, and flaky skin on the back, nosebleeds, ocular inflammations, or kidney problems may not be constant, but should also point to leishmaniosis for dogs that have traveled in enzootic areas. To confirm diagnosis in a dog with suspicious symptoms (clinical symptoms and travel to applicable area), the veterinarian can detect the parasite using a microscope (studying lesions and punctures of ganglions or bone marrow), or by looking for evidence of its passage (searching for anti-leishmania antibodies in the blood).
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As with most serious parasitic diseases (dirofilariosis, piroplasmosis, etc.), the best prevention consists in avoiding contact with a vector. There is currently no vaccine available, so certain precautions should be taken whenever a dog lives in or is traveling through an enzootic zone during competition: Avoid taking the dog out after dusk (because sandflies are more active at night) and use insecticides, especially on areas of the body that are particularly at risk (the nose). No treatment currently prevent a recurrence of the disease: Dogs can develop leishmaniosis throughout their lives regardless of how many times they have contracted it already.
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Coccidiosis
Coccidiosis is a parasitic digestive disorder caused by the presence of microscopic, single-celled parasites called coccidia. There are several types of coccidia in dogs, such as Isospora (transmitted from one dog to another), cryptosporidia (can be transmitted by an intermediary mammal such as rodents, cats, cattle, etc.), and sarcosporidia (transmitted by consumption of flesh from a contaminated animal). Isispora coccidiosis is by far the most common in dog breeding.
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The disease most often affects puppies during weaning and the stress and change in lifestyle for the young dogs are traditionally considered to be favorable factors for its development (mother's milk is a unfavorable factor for the development of coccidia). It manifests as fresh blood (red) or digested blood (black) in mucus and excrement, which will be diarrhea-like and yellowish. Suspicions of coccidiosis should be confirmed by a veterinarian through stool samples from afflicted puppies. It is preferable to perform this study one to two weeks after the first symptoms have appeared to avoid false negative results.
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Coccidiosis is rarely serious, but can cause immunodepression problems that will be exaggerated through sports, considerably increasing the overall risk of infection. Prevention involves isolating maternity in a breeding situation, taking excrement samples twice daily in the yard, and by regularly and effectively disinfecting the environment (steam is very effective). Treatment should be early and complete, using sulfa drugs and related medicines and certain (anti-adhesive) dressings that prevent the parasites from attaching and penetrating the intestinal cells.
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Specific examination of these parasites also stresses the importance of appropriate hygienic and sanitary prevention in the dogs' daily environment.
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