Information on Protozoans, Rickettsia, Babesiosis, Ehrlichiosis, Leishmania, Lyme Disease, Toxoplasmosis.

Most dog owners are unfamiliar with protozoans and rickettsia Is - organisms that are strictly speaking neither bacteria, viruses, fungi nor parasites - because they rarely affect dogs in Britain. However, several of the conditions they cause are widespread on mainland Europe, and are being seen more commonly in this country as more pets travel abroad following the introduction of the Pet Travel Scheme.

What are they?
The organisms discussed in this article range from protozoans (which, like bacteria, are single-celled organisms resembling our own cells in size and structure) to the smaller rickettsials which have a far simpler structure and are around a third of the size of our cells. Both have a central nucleus containing genetic material surrounded by a cell membrane and, unlike viruses, both of these types of organisms are able to reproduce by themselves. Several of the diseases caused by these organisms are zoonotic (they can be transmitted to people) so have human public health and safety implications as well as those for the affected dog. And the one thing all of these diseases share is that they are difficult to treat successfully.

How do they occur?
Like bacterial and viral diseases, these conditions are infectious diseases spread from one dog to another. However, while bacterial and viral conditions are passed directly between dogs, the usual method of transmission for many of these diseases involves an insect which acts as the carrier of  the organism from one dog to another. And it is these insects that define where the diseases are prevalent; the sand flies that carry leishmania and the particular types of tick that carry ehrlichia and babesia are generally found in Europe, so that is where the conditions are common.

Coming from the UK, our dogs have no natural resistance to these conditions and so are particularly susceptible to them if they travel in Europe. Also, it appears that warmer weather in the UK means that some of these insect vectors are starting to live here (even before the Pet Travel Scheme began there was evidence of some European ticks living in the countryside near quarantine kennels), and together with the increased travel of dogs, this may result in the diseases becoming a risk even for those dogs that don't leave the UK. A range of diseases can be caused by these organisms in susceptible individuals, and treating ill dogs is complicated by the fact that not all dogs that come into contact with them develop disease. Those that do vary enormously in the symptoms they show. Diagnosis of these conditions is often difficult, and not all affected dogs respond well to treatment. Severe disease is, however, thankfully rare, but those that can occur are:

Babesiosis.
Particularly prevalent in France, but seen throughout Europe, babesiosis is a protozoal disease which is carried by ticks and can be fatal. The Babesia organism is passed to the tick when it bites an infected dog or fox, and then develops in the salivary gland of the tick before being transmitted to the next dog it feeds upon.

Babesia targets red blood cells and causes them to disintegrate, so that the affected dog suffers from anaemia and associated symptoms of pallor, weakness, lethargy, liver and spleen abnormalities and even death. It can be diagnosed by examining a blood smear under a microscope for infected red blood cells. Treatment is available but it carries the risk of side effects and is often not curative. Instead a carrier state may develop where the dog remains infectious (though it can only spread the disease if it is bitten by the right sort of tick) and symptoms of disease flare up from time to time.

Ehrlichiosis.
Also carried by ticks, ehrlichiosis is a disease caused by Ehrlichia, a rickettsial organism that is found in Mediterranean Europe, Africa and the USA, and may occur together with babesiosis.
The organism passes into the dog as the tick feeds, and targets a particular type of cell in the circulation and the tissues, leading to symptoms that progress from non-specific malaise and a high temperature to anaemia and immune suppression. This can be a difficult condition to diagnose as it can be hard to identify the organism in blood or tissue samples, but blood tests can be helpful.
Antibiotics and supportive treatment can result in recovery, but not all affected dogs make good progress.

Leishmania.
Leishmania is a particularly concerning protozoan disease because humans can catch it too. It's transmitted by sandflies found in Mediterranean Europe, and in dogs causes symptoms including weight loss, enlargement of the lymph nodes (glands), skin disease, lameness due to joint pain, eye disorders and kidney damage.
Even in mild cases, the risks to human health and the variable response to treatment mean that there is a case for putting affected dogs to sleep if this condition is diagnosed. Salmon poisoning
Dogs traveling to the USA can come into contact with a condition known as salmon poisoning if they eat salmon infected with a rickettsial called Neorickettsia helminthoeca. Fever, loss of appetite and diarrhoea are seen and the condition can be fatal. This condition is not seen in Europe.

Lyme disease.
British ticks are thankfully not involved in transmitting Babesia and Ehrlichia, but there is one condition they can pass to dogs and that is borreliosis or Lyme disease. This can also affect people and horses and so care should be taken to avoid tick bites. Symptoms include joint pain and lameness, heart disease, kidney problems and even nervous symptoms. This condition is treatable with long courses of antibiotics, but some animals have long-term problems such as arthritis if the disease isn't diagnosed and treated promptly, and diagnosis can be difficult.

Toxoplasmosis.
This is a relatively rare cause of disease in dogs in the UK despite the organism being fairly widespread; cat faeces, raw meat and sheep can all act as sources of infection.
The Toxoplasma protozoan can damage almost any part of the body so a range of symptoms can result, though liver disease and nervous symptoms are most commonly seen. This disease is zoonotic and is particularly dangerous for an unborn baby. Treatment is available for this condition but long courses are necessary and not all individuals respond well.

Diagnosis and treatment.
Diagnosis of these conditions is difficult because the range and severity of symptoms dogs show vary so much, and the organisms themselves can be very difficult to identify in samples taken. Treatment is also troublesome. Protracted courses of antibiotics or other medicines can be successful, but some dogs suffer side effects of treatment or remain infected despite treatment.

Avoidance.
Vaccination is unfortunately unavailable for these conditions in dogs although a toxoplasmosis vaccine for sheep is available. Since treatment is so unpredictable, avoidance of contact with the organisms in question. is advisable. Effective anti-tick measures are of paramount importance for dogs traveling abroad, or living in forested areas of the UK where ticks carry Lyme disease. In areas of Europe where leishmania is a big problem most vets advise the use of deltamethrin-impregnated collars, which help to protect against sandflies.

To protect against toxoplasmosis, access to cat faeces should be prevented and the feeding of raw meat (especially Iamb) should be avoided.

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