Canine Ehrlichiosis

The Ehrlichiosis the dog (also Tropical Canine Pancytopenia , "tick fever") is an acute to chronic infectious disease caused by the bacterium Ehrlichia canis (named after its discoverer, the German physician Paul Ehrlich is caused). The classic Ehrlichiosis caused by Ehrlichia canis is endemic in the tropics and subtropics as well as in the Mediterranean area (" Mediterranean disease "), so that dogs are particularly at risk when traveling to these regions on holiday. The pathogens attack the white blood cells (especially monocytes andLymphocytes ). The disease was first observed in a dog in Algeria in 1935. During the Vietnam War, numerous dogs belonging to American soldiers fell ill.

The "granulocytic Ehrlichiosis" caused by Anaplasma phagocytophilum is called canine anaplasmosis according to the more recent systematics .

Pathogen and disease development

The causative agent of classical Ehrlichiosis (monocytic and lymphocytic Ehrlichiosis) is Ehrlichia canis , an obligatory intracellular bacterium from the order of the Rickettsiae . The brown dog tick ( Rhipicephalus sanguineus ) in particular is the vector and reservoir for E. canis . The ticks can harbor the pathogen for up to five months. The pathogen is presumably a primary tick parasite and affects the tick's blood cells , midgut cells and salivary gland cells. Dogs are only secondary hosts and become infected through the tick saliva when they suckle. The transmission from the tick to the dog occurs relatively quickly, it can take place as early as three hours after the tick has attached.

E. canis binds to surface glycoproteins on monocytes . The pathogen reaches these blood cells via endocytosis and prevents the endosomes from fusing with lysosomes and thus preventing them from being destroyed. In the cells, the bacterium multiplies in the form of a division into two. As a result of the infection, E. canis suppresses the defense function of the monocytes. Although the body produces high levels of antibodies , these do not have a protective effect. Immune complexes and the increased viscosity of the blood as a result of the increased gamma globulins also play a role in the development of the disease.

Ehrlichiosis can be caused by other so-called secondary infections, e.g. B. be complicated with babesia and hemobartonellosis . Human infections by the pathogen occur, but presumably only through transmission by ticks; dog-to-human transmission is unlikely. The extent to which autochthonous infections also occur in Germany due to the spread of this tick has not yet been fully established. However, it cannot be ruled out, so that the Ehrlichiosis can no longer be viewed as a typical "motion sickness".

Symptoms

The symptoms are mostly unspecific and very diverse. All breeds of dogs, especially puppies, are affected.

After an incubation period of just under three weeks, the animals show in the acute phase constantly recurring fever , nosebleeds ( epistaxis ), mucous-purulent nasal discharge, vomiting , exhaustion, 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 around two to four weeks and can move into a subclinical stage over weeks or years . In this, the animals remain infected, but show no symptoms. Thrombocytopenia and high gamma globulin levels can be detected in the laboratory .

After the symptom-free phase, the chronic stage begins with bleeding and edema , fatigue, emaciation, anemia , enlarged spleen ( splenomegaly ), joint diseases ( polyarthritis ) and meningoencephalitis with cramps and paralysis . However, the classic picture with a strongly increased tendency to bleed occurs in only about a quarter of the cases.

pathology

Pathologically and anatomically, there are numerous small hemorrhages ( petechiae , ecchymoses ) on the surface of internal organs. The liver and spleen are usually enlarged. The lymph nodes are enlarged and have a brownish discoloration. Pathohistologically, the liver and spleen show lymphoreticular hyperplasia . Vasculitis and plasma cell infiltrates are evident in the kidney . Interstitial pneumonia can occur in the lungs .

diagnosis

The diagnosis cannot be made clinically. Other infectious diseases ( babesiosis , hemobartonellosis , borreliosis ), which can also be associated with Ehrlichiosis as secondary infections, as well as immunologically induced thrombocytopenia come into question in the differential diagnosis .

Laboratory diagnostics can be used:

• Pathogens can be detected in the blood or in samples from the lungs and other organs using Giemsa staining and immunofluorescence tests . The monocytes and lymphocytes show a typical morula structure, but not very numerous in the Giemsa stain. The optimal detection is possible 13 days after the infection. The characteristic morulae occur in Ehrlichia ewingii infections in neutrophils and eosinophils.
• Thrombocytopenia , hyperglobulinemia , anemia, and neutropenia can aid the diagnosis.
• E. canis can be detected in tissues via PCR and in situ hybridization .
• Detection of antibodies in serum : A titer can be detected 7–21 after infection and up to 16 months after the pathogen has been eliminated. A titer of 1:10 or higher is proof. It can be negative in the early stages of infection. In addition, possible cross-reactions, e.g. B. with Anaplasma phagocytophilum should be considered.

treatment

Therapy takes place with antibiotics such as doxycycline , tetracycline and oxytetracycline over two weeks. Seropositive animals should be isolated.

Prevention can be achieved through regular control and immediate removal of ticks or through the use of tick-repellent (e.g. permethrin ) or tick-killing agents such as Fluralaner .

Individual evidence

1. ^ Entry on Ehrlichia in Flexikon , a wiki from DocCheck , accessed on November 26, 2015.
2. ↑ ^{a b c} Nico Pantchev: Tick-borne travel infections in dogs: Ehrlichiosis and babesiosis . In: Veterinary mirror . tape 4 , 2012, p. 162-170 .
3. ^ ^{A b c d e} Carlheinz Wiedemann: The canine Ehrlichiosis, an introduced infection . In: Small Animal Practice . tape 37 , 1992, pp. 319-325 .
4. ↑ Stefan Pachnicke: Vector prophylaxis : Indirect reduction of the risk of transmission for CVBD pathogens. In: The practical veterinarian . tape 97 , no. 5 , 2016, p. 468-469 .
5. ↑ ^{a b} J. Jensen et al .: Occurrence of Ehrlichia canis in dogs in Germany? In: Tierärtl. Practice . tape 35 , 2007, p. 123-128 .

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