The control of lymphosarcoma/leukaemia and feline leukaemia virus

This article discusses a removal programme designed especially for catteries and so–called multiple–cat households in an effort to control lymphosarcoma/leukaemia in cats and transmission of FeLV (feline leukaemia virus).
The removal programme calls for: annual testing of all stud cats; testing of all contacts of a FeLV–positive cat during the previous 2 years; testing of imported cats; and isolation of FeLV–positive cats or, if this is impossible, euthanasia. The FeLV antigen can be demonstrated in cats by the indirect immunofluorescence antibody (IFA) test.
The results of a removal programme carried out over a 4–year period in a large Dutch cat club are discussed. The percentage of FeLV–positive catteries decreased from 11 –5% during the first half of 1974 to 21% during the latter half of 1977; during the same period the percentage of FeLV–positive cats and stud cats decreased from 4–9% and 5–9%, respectively, to 1–2% and 1–0%, respectively.
It is concluded that the recommended removal programme can be carried out without difficulty and produces good results.     

Chronic granulocytic leukaemia/ eosinophilic leukaemia in a dog?

A suspected case of chronic granulocytic leukaemia (chronic myelogenous leukaemia) with eosinophil differentiation and hepatic involvement is described in a 3–5-year-old rottweiler dog. Neoplastic eosinophilic infiltrates were also present in the lungs, kidneys, mesenteric lymph nodes and peribronchial and prester-nal lymph nodes. Both pleural and abdominal effusions contained predominantly eosinophils and their precursors. The bone marrow showed an increase in the myeloid to erythroid ratio and an increase in the marrow granulocyte reserve. The majority of cells identified within the bone marrow were of the eosinophil series. Myelocytes and promyelocytes predominated.     

Feline leukaemia virus testing

Extract

Sir:- In September 1981 we published the results of leukaemia virus (Felv) testing of cats in New Zealand.⁽²⁾ In addition we detailed recommendations for Felv testing of cats in this country. These recommendations were revised and updated in a second letter to the Journal in 1982.⁽³⁾ Since then a further 465 cats have been tested at Massey University using the leukassay test (ELISA) (Leukassay F, Pitman Moore).     

Control of feline leukaemia virus

Feline leukaemia virus (FeLV) usually occurs in its natural species, the domestic cat. FeLV is also important to human individuals as a comparative model, as it may cause a variety of diseases, some malignant and some benign, such as immunosuppression, which bears a resemblance to AIDS (acquired immune deficiency syndrome) in man. FeLV is transmitted among cats by contagion. The main sources of infection are persistently infected carrier cats which continuously excrete virus. Dissemination of FeLV among cats may be prevented by identifying infected carrier cats and removing them from contact with non-infected cats. Removal programmes using indirect immunofluorescence antibody tests were applied successfully in The Netherlands. The proportion of FeLV-positive cats decreased from 9% in 1974 to approximately 3% in 1985 during such a programme. The results of a removal programme carried out in a catbreeders' society were even better: the incidence of cats positive for FeLV decreased from 11% in 1974 to less than 2% within 4 years. None of the cats tested in this society has been found to be positive for FeLV since 1984. Besides removal programmes, other methods of control, such as pre-exposure treatment, were developed to prevent the spread of FeLV. We attempted to protect kittens against oronasal infection with FeLV by treatment with virus-neutralizing (VN) monoclonal antibodies (MoAbs) directed against an epitope on the viral glycoprotein gp70. However, no protection was achieved. It is unlikely that the amount of VN antibodies, the mode and route of their application or the infectious dose of FeLV used can account for this failure. Other possible explanations for the lack of protective effect are that (i) the restricted epitope specificity of the MoAb preparation used may have led to selection of neutralization-resistant virus mutants, or (ii) other mechanisms than virus neutralization (complement-mediated lysis, antibody-dependent cell cytotoxicity), that may be involved in protection, function less efficiently with MoAb. However, in the light of our finding that an early anti-idiotypic response is observed in all cats following administration of the MoAb preparation, the rapid clearance of anti-FeLV MoAb from the circulation is a more likely explanation. Efforts were further made to develop a vaccine for controlling FeLV infection. The immunostimulating complex vaccine (FeLV-ISCOM vaccine), a subunit vaccine in which FeLV gp70 is presented in a particular manner, looks promising. The protective effect of FeLV-ISCOM vaccine was studied by vaccinating six 8-week-old SPF cats with ISCOM, followed by oronasal challenge with FeLV.(ABSTRACT TRUNCATED AT 400 WORDS)     

Lymphoid leukaemia in a cow

An 18-month old Friesian heifer which had lost condition and had diarrhoea for several weeks was diagnosed by haematological and pathological examinations as having lymphocytic leukaemia. True lymphatic leukaemia has not previously been described in cattle and does not readily fit into presently accepted classifications of bovine leukosis.     

Eosinophilic leukaemia in a cat

A 14-year-old female domestic shorthair cat was presented to Tehran University Veterinary Teaching Hospital for a persistent fever, anorexia, intermittent vomiting, weight loss and weakness. The main clinical signs were pale mucous membranes, dehydration and splenomegaly. The complete blood count and serum biochemistry tests revealed non-regenerative anaemia, thrombocytopenia and increased alkaline phosphatase (ALP) activity. An enzyme-linked immunosorbent assay (ELISA) test for feline leukaemia virus was negative. Blood film and bone marrow examination revealed a large number of immature eosinophils with variable sizes and numbers of faintly azurophilic granules. Cytochemical staining of blood film demonstrated 70% positive cells for ALP activity. Four percent CD34 positive cells were detected by flow cytometry. As eosinophilic leukaemia is difficult to identify by light microscopy, well-defined diagnostic criteria and the use of flow cytometry and cytochemical staining can improve the ability to correctly diagnose this type of leukaemia in cats.     

Lymphoid leukaemia in a cow

An 18-month old Friesian heifer which had lost condition and had diarrhoea for several weeks was diagnosed by haematological and pathological examinations as having lymphocytic leukaemia. True lymphatic leukaemia has not previously been described in cattle and does not readily fit into presently accepted classifications of bovine leukosis.