Ehrlichiosis (canine)

Ehrlichiosis the dogs (also Tropical Canine Pancytopenia, " tick fever " ) is an acute to chronic infectious disease caused by the bacterium Ehrlichia canis. The classic, caused by Ehrlichia canis ehrlichiosis is endemic in the tropics and subtropics and the Mediterranean, so that dogs are at risk, especially during holiday trips to these regions. The pathogens infect the white blood cells (mainly monocytes and lymphocytes). The disease was first observed in 1935 in a dog in Algeria. During the Vietnam War affected many dogs of American soldiers.

Caused by Anaplasma phagocytophilum " granulocytic ehrlichiosis " is referred to by newer system as Canine anaplasmosis.

Pathogen and disease development

The causative agent of classical ehrlichiosis (mono-and lymphocytic ehrlichiosis ) is Ehrlichia canis, an obligate intracellular bacterium from the order of rickettsiae. Especially the brown dog tick ( Rhipicephalus sanguineus) is a carrier and reservoir for E. canis. The ticks can harbor the pathogen up to five months. The pathogen is believed to be a primary tick parasite and infects blood cells, midgut cells and salivary gland cells of the tick. Dogs are only secondary hosts and become infected during suckling on the tick saliva.

E. canis binds to surface glycoproteins of monocytes. About endocytosis of the pathogen enters these blood cells and prevents the fusion of endosomes with lysosomes and thus its destruction. In the cell there will be a proliferation of the bacterium in the form of a bifurcation. By E. canis infection suppresses the immune function of monocytes. Although the body produces high levels of antibodies, but they do not act protectively. Immune complexes and the increased viscosity of the blood due to increased gamma globulins also play a role in the pathogenesis.

A ehrlichiosis can be complicated by other, so-called secondary infections, such as Babesia and haemobartonellosis. Human infections by the pathogen occur, but probably only by transmission by ticks, a dog -human transmission is unlikely. Extent by the spread of this tick on Germany, autochthonous infections occur, is not yet fully secured. However, they are by no means excluded, so that the ehrlichiosis can not be regarded as typical " motion sickness ".

Symptoms

The symptoms are usually nonspecific and very diverse. All breeds of dogs, especially puppies, are affected.

After an incubation period of three weeks, the animals show in the acute phase of recurrent fever, nosebleeds ( epistaxis), mucopurulent nasal discharge, vomiting, fatigue, shortness of breath, swelling of the lymph nodes (generalized lymphadenopathy ), and possibly central nervous disorders such as muscle twitching and hypersensitivity. The acute phase lasts about two to four weeks and can go on for weeks or years in a subclinical stage. In this, the animals remain infected but show no symptoms. Laboratory diagnosis can be detectable thrombocytopenia and high Gammaglobulinspiegel.

After the asymptomatic phase, the chronic stage (anemia), spleen enlargement begins with hemorrhage and edema, fatigue, emaciation, anemia (splenomegaly ), joint disease ( arthritis ) and encephalitis with convulsions and paralysis. The classic image with greatly increased bleeding only occurs in about one quarter of the cases.

Pathology

Pathologically, there are numerous small hemorrhages ( petechiae, ecchymosis ) at the surface of internal organs. Liver and spleen are usually enlarged. The lymph nodes are enlarged and discolored brownish. Histologically, the liver and spleen show a lymphoreticular hyperplasia. In the kidney, show vasculitis and plasma cells. In the lung, an interstitial pneumonia occur.

Diagnosis

Clinically, the diagnosis is not to ask. The differential diagnosis of other infectious diseases ( babesiosis, haemobartonellosis, Lyme disease ), which can be associated as a secondary infection with ehrlichiosis, as well as an immunologically induced thrombocytopenia in question.

Laboratory diagnosis can be used:

• Detection of pathogens from blood or samples from the lungs and other organs, be a Giemsa staining and immunofluorescence assay. However, monocytes and lymphocytes show not very numerous typical morula structure in which Giemsa staining. The optimum detection is possible 13 days after infection. The characteristic morulae occur in Ehrlichia ewingii - infections in neutrophilic and eosinophilic granulocytes.
• Thrombocytopenia, hyperglobulinemia, anemia and neutropenia can support the diagnosis.
• By PCR and In Situ Hybridization E. canis can be detected in tissues.
• Detection of antibodies in serum: A is 7-21 titer detectable after infection and up to 16 months after the elimination of the pathogen. A titer of 1:10 or higher is conclusive. In the early phase of the infection, it can be negative. In addition to possible cross- reactions be considered, eg with Anaplasma phagocytophilum.

Treatment

Treatment is by antibiotics such as doxycycline, tetracycline and oxytetracycline over two weeks. Seropositive animals should be isolated.

A prevention can take place (eg permethrin ) regular inspection and prompt removal of ticks or by the use of tick repellents.