Feline Infectious Anemia
The feline infectious anemia (abbreviation FIA , synonyms: haemobartonellosis , hemolytic anemia ) is a worldwide occurring bacterial infectious disease of cats . It is caused by hemotropic mycoplasmas , which are bacteria that attack the red blood cells ( erythrocytes ). In healthy animals, the infection is mostly harmless and has no clinical symptoms . However, in weak animals can one acute or chronic anemia ( anemia cause). The disease is curable, but the animals remain lifelong carriers of the pathogen and thus represent a source of infection to other cats. In practice, it is particularly as a concomitant disease of viral diseases , which leads to a further deterioration of health, and as a potential danger with blood transfusions in Cats matter. Since the pathogens have a high host specificity, humans and animals other than cats are not susceptible to this disease.
Pathogen and Pathogenesis
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Several pathogens of feline infectious anemia are distinguished, which have been assigned taxonomically to the mycoplasmas by recent molecular biological studies . The large form is now called Mycoplasma haemofelis , the name Mycoplasma haemominutum was suggested for the small form . Both pathogens were to 2001 as Haemobartonella felis (hence the name "haemobartonellosis") or Eperythrozoon felis designates and the rickettsial counted, the former "Ohio isolate" corresponds Mycoplasma haemofelis , the "California isolate" Mycoplasma haemominutum . In 2005 a third pathogen was isolated, for which the name Mycoplasma turicensis was proposed. The three pathogens are summarized as hemotropic mycoplasmas . It is an obligate epicellular (only able to survive on living cells ), gram- negative bacteria. The pathogen most frequently detected in all studies is Candidatus Mycoplasma haemominutum .
The pathogens attack the red blood cells and damage the membrane. The damaged erythrocytes are then phagocytosed by white blood cells (especially monocytes , less often by neutrophils ) . Much of the erythrocyte elimination occurs through the macrophages in the spleen , which is why cats with the spleen removed ( splenectomy ) are particularly at risk. During the passage through the red pulp of the spleen (cf. anatomy of the spleen ), the location of the excretion of damaged or aged erythrocytes, the detachment and phagocytosis of the mycoplasmas without phagocytosis of the erythrocytes was also observed. The amount of red blood pigment ( hemoglobin ) released during the breakdown of erythrocytes ( hemolysis ) can usually be processed by the liver . Very rarely does the amount of pigment in the blood increase ( hemoglobinemia ) and then excretion in the urine ( hemoglobinuria ).
For the pathogenesis it is also important that the immune system not only produces antibodies against the pathogen, but also against the erythrocytes themselves, so that the disease is in part an autoimmune disease .
Epizootiology
The disease was first observed in South Africa in 1942 . However, hemotropic mycoplasma occurs latently in many cats worldwide ; these animals represent the pathogen reservoir. In addition to domestic cats , the pathogen has also been detected in tigers . In a study on the epizootiological situation in Switzerland ( Lit .: Willi, 2006), around nine percent of domestic cats were infected with hemotropic mycoplasma. So far there have only been individual case reports on acute illnesses in Europe , including some from Germany and Switzerland.
The natural transmission route is unknown. It is assumed that blood-sucking parasites ( fleas , ticks and lice ) are involved, so they represent a feline vector-borne disease , or bite and scratch injuries. A transfer of the she-cat on the puppies is also possible, however, is still unclear whether these via the breast milk ( lactogen ) or even before birth via the placenta ( transplacental done). Another method of transmission is via blood transfusions ( iatrogenic infection). The possibility of peroral as well as intraperitoneal transmission has also been demonstrated experimentally .
Clinical picture
The incubation time for experimental parenteral infection is between 2 and 17 days, for experimental peroral infection between three and seven weeks.
As a rule, the infection is symptom-free. Clinically, an illness usually only occurs when the immune system is weakened , for example due to stress or other illnesses, especially in feline leukemia and immunodeficiency syndrome in cats . Young animals (under 3 years of age) are often affected by the disease. In addition, cats that roam free, inadequately vaccinated animals and animals that have already suffered from abscesses caused by cat bites are considered risk groups. The sex, the number of cats living in the household and the infestation of the animals with fleas are not significant risk factors.
The acute FIA is manifested by fever , reduced food intake , general weakness, pale mucous membranes, and enlarged spleen . A jaundice or hemoglobinuria rarely occurs very. After surviving the first acute phase of the disease, the symptoms reappear in bursts (intermittently) with each new bacteremia . In between there are symptom-free intervals. In rare cases, skin irritations such as hyperesthesia and hair loss occur.
In chronic FIA, the clinical symptoms are less pronounced, and they are often absent entirely. The body temperature is normal or slightly decreased.
Laboratory diagnostic findings
A medical laboratory examination reveals a macrocytic, normochromic or hypochromic hemolytic anemia , which can be characterized by three main criteria (also: major criteria).
- 1. Main criterion: A slide agglutination test ("biological Coombs test") can be carried out as a simple laboratory test: a drop of heparinized blood is smeared onto a slide and examined under the microscope . In the positive case, the erythrocytes clump ( agglutinate ). In order to distinguish this finding from the physiologically occurring " roll formation " of red blood cells, a positive test should be repeated with the addition of a drop of physiological saline solution . By using pre-chilled slides, the presence of cold agglutinins can even be detected.
- 2. Main criterion: In the blood count , a decrease in the number of red blood cells, a so-called anemia can be determined. This is a regenerative anemia; H. new erythrocytes are constantly being reproduced in the bone marrow . Since the bone marrow's capacity to regenerate has been exceeded, immature erythrocytes ( reticulocytes , possibly normoblasts ) are also released into the blood. The erythrocytes have different cell sizes ( anisocytosis ), enlarged erythrocytes appear ( macrocytosis ) and the erythrocytes are colored differently ( polychromasia , a typical sign of immature erythrocytes). Thus, the second major criterion is (strongly) regenerative, macrocytic, hypochromic anemia with spherocytes . An increased number of white blood cells ( leukocytosis , mostly as neutrophilia ) is also common.
- 3. Main criterion: Due to the changes in the erythrocyte membranes, the direct Coombs test is positive.
Other possible changes in the blood are an increased level of protein ( hyperproteinemia ), bilirubin ( hyperbilirubinemia ) and nitrogen-containing breakdown products ( azotemia ) as well as increased activity of the enzymes ALAT and LDH .
Differential diagnoses
The clinical picture is not very meaningful. In the case of fever and anemia, however, this disease must always be included in the diagnostic spectrum.
Other infectious diseases that are associated with anemia are feline leukemia (FeLV), infectious peritonitis (FIP), and feline aids (FIV), but non-regenerative anemia predominates. Anemia can also cause severe infestation with endo- or ectoparasites . The Feline babesiosis (pathogen Babesia felis ) is not clinically distinguished from the FIA and is partly associated with it before. The cytauxzoonosis (infection with Cytauxzoon felis ) plays in Central Europe not matter but is used primarily in the southern United States before.
The significance of autoimmune hemolytic anemia (AIHA) in cats is still unclear. So far it has only been described in connection with the FIA itself and feline leukosis.
Furthermore, non- infectious causes of anemia must be ruled out, such as iron deficiency and chronic blood loss ( stomach ulcers , chronic bladder infections ). An erythropoietin deficiency comes from a. in chronic kidney failure , which is common in older cats. Damage to the bone marrow (for example due to cytostatics or heavy metals ) causes non-regenerative anemia. Various drugs are relatively poorly tolerated by cats and can cause anemia as side effects , such as azathioprine , griseofulvin , paracetamol , phenazopyridine , phenylbutazone and propylthiouracil .
Genetically determined enzyme defects ( pyruvate kinase deficiency and phosphofructokinase deficiency) can also cause anemia, for which DNA evidence exists.
diagnosis
An exact diagnosis of feline infectious anemia is only possible through the detection of the pathogen. Regenerative anemia supports the diagnosis. Non-regenerative anemia caused by mycoplasma probably only occurs with simultaneous infection with the feline leukosis virus (FeLV), but feline leukosis is the most common underlying disease that promotes FIA.
The pathogen can be detected by staining blood smears . If possible, fresh capillary blood should be used for the examination, as the pathogens can also detach themselves from the erythrocytes, especially when chelating anticoagulants ( e.g. EDTA ) are added. In addition, blood samples must be taken and examined over several days, as the pathogen only occurs in bursts in the blood. During the microscopic examination, the pathogens can be detected as small cocci, about 0.1 to 1 μm in size, rods or rings in the periphery of the about 5 to 7 μm in size erythrocytes. With antibiotic pretreatment, the pathogen detection in the blood can be negative. In addition, artifacts and, depending on the color, erythrocyte inclusion bodies such as Howell-Jolly (remnants of the cell nucleus of normally nucleated erythrocytes) or Heinz bodies ( denatured hemoglobin, occurs physiologically in cats) can be mistaken for mycoplasmas. The certainty of detection via a blood smear is given as only about 50%.
Much safer and more specific is the pathogen detection using the polymerase chain reaction (PCR), which is now offered by all major testing facilities.
treatment
Clinically manifest disease is fatal in about 30% of cases if no treatment is given, with the cause of death being the severe anemia caused by the pathogen . The hemotropic mycoplasmas are sensitive to doxycycline and other tetracyclines as well as fluoroquinolones ( enrofloxacin , marbofloxacin and pradofloxacin ). The antibiotic therapy should be about two to three weeks. Supportive therapy to stabilize the general condition is recommended. In severe anemia, blood transfusions are indicated (about 40 to 50 ml of blood, the donor animals must be tested for the absence of pathogens).
Since the damaging effect of the pathogen occurs partly through immune-mediated mechanisms, the administration of prednisolone is recommended in severe illness .
After successful treatment, however, the cats usually remain carriers of the pathogen for life.
prevention
As the exact route of transmission is unknown, targeted prophylaxis is difficult. Regular prevention and control of ectoparasites is recommended . Depot preparations are suitable for this. Cats that are to serve as blood donors must first be thoroughly examined for the possible presence of the pathogen.
literature
- JB Messick: New perspectives about Hemotrophic mycoplasma (formerly, Haemobartonella and Eperythrozoon species) infections in dogs and cats . In: Vet. Clin. North Am. Small. Anim. , Volume 33, 2003, pp. 1453-1465. PMID 14664208 .
- H. Neimark, KE Johansson, Y. Rikihisa and JG Tully: Revision of haemotrophic Mycoplasma species names. In: International Journal of Systematic and Evolutionary Microbiology. Volume 52, 2002, pp. 683-683. PMID 11931184 .
- JE Sykes: Feline hemotropic mycoplasmosis (feline hemobartonellosis) . In: Vet. Clin. North Am. Small. Anim. , Volume 33, 2003, pp. 773-789. PMID 12910743 .
- S. Tasker, MR Lappin: Haemobartonella felis: recent developments in diagnosis and treatment. In: J. Fel. Med. Surg. , Volume 4, 2002, pp. 3-11. PMID 11869051 .
- Christiane Weingart and Barbara Kohn: Hemotropic mycoplasma in cats: new aspects of prevalence, clinical features, diagnosis, therapy and prognosis . In: Kleintierpraxis , Volume 60, 2015, No. 11, pp. 590–602.
- B. Willi et al .: Prevalence, risk factor analysis, and follow-up of infections caused by three feline hemoplasma species in cats in Switzerland. In: J. Clin. Microbiol. , Volume 44, 2006, pp. 961-969. PMID 16517884 .
