Feline Leukemia Virus - Essay Example

Feline Leukemia Virus (FeLV) The Feline Leukemia Virus is a retrovirus that affects several species of cats, Felicis Sylvestris being one of them. The genetic information of the virus is stored in the form of RNA(Ribo Nucleic Acid), which is why it is referred to as a retrovirus. The occurrence of this disease in cats varies in accordance with their environment. Studies have demonstrated that nearly 3% of the household cats are infected with this virus. This number increases to 11% for the stray or outdoor cats. In multi cat households, this figure reaches a staggering 70% (Little,2006) Researches have also made it clear that cats living in urban areas (40%) are more likely to be infected than the ones living in rural areas(6%) (Little, 2006) The FeLV virus is a fragile virus and can survive for only two hours in a dry environment and 48 hours in damp and moist surroundings. Though it is contagious, it can only be transmitted among cats; it cannot potentially infect humans. Within cats, it is transmitted via intimate moist contact through licking, biting, grooming or eating from the same source. It can also be transmitted through urine, feces and milk. It is also transmitted from an infected mother to her new born kitten (Hoover & Mullins, 1991) It is usually categorised in the following four classes- FeLV A, B, C and T. Out of these, only FeLV A is transmissible among cats, while the others arise de novo. While FeLV A causes severe immunosuppression, FeLV B and C cause neoplastic diseases and anemia respectively (Poulet et al,2003) Signs and Symptoms In the initial stages of infection, the signs and symptoms of FeLV are not very pronounced. As the infection progresses, certain symptoms become more obvious. These include: Loss of appetite accompanied with severe weight loss. High fever, deteriorating condition of the fur coat. Inflammation of the lymph nodes. Gingivitis i.e. inflammation of the gums and stomatitis i.e. inflammation of the mouth. Persistent infection in the respiratory and urinary tract. Neurological disorders like seizures. Progression Once a cat is exposed to the virus, there are four possible consequences, depending on the response of the immune system. In about 30% of the cats, the virus evokes a strong immune response, which in turn extinguishes the virus. In another 30% the cats’ immune system does not produce an immediate immune reaction. At the same time though, the virus does not manifest its potential effects. It resides safely in a dormant state in the cats’ bone marrow. It might express itself later or may remain dormant forever. In the remaining 40% of the cats, the virus is successful and the cats become infected. (Hoover, Mullins, 1991) Once the virus actively infects a cat, it can have hazardous effects. It can lead to cancerous diseases like leukemia and lymphosarcoma. It also leads to a generalized suppression of the immune system, and may also cause reproductive ailments. Besides these, it also damages the liver and intestine, and is also capable of causing blood infections (Little,2006) Tests for Diagnosis of FeLV A few tests have been devised for the detection and diagnosis of FeLV in cats. The most popular out of these screening test is ELISA( Enzyme Linked Immunosorbent Assay). This test is used as a preliminary one, while the IFA(Indirect Immunoflorescent Antibody Assay) is usually carried out for a final diagnosis (Richards et al,2003). In some cases, the PCR or the Polymerase Chain Reaction might also be recommended. Treatment Unfortunately, there aren’t any medically proven treatment options available for FeLV infected cats. Though some methods have been devised, none of them have yielded very encouraging results. One such treatment option is the Lymphocyte T Cell Immune System Modulator. This method was partially recognised by the United States Department of Agriculture when it issued a conditional license to practice this method in 2006 (Richards et al, 2006) The modulator stimulates the immune system through CD4 Lymphocytes, which are powerful regulators of immune response.(Beadrsley et al,1983). Thus, the modulator increases the production of lymphocytes, thus boosting the immune reaction. Besides this, several other treatment schemes have surfaced which also focus on augmenting the immune response. Administrations of interferons, which are otherwise produced naturally by the body against he viruses, is one such method. Anti viral drugs such as AZT(Azidothymidine) is another mode of treatment (Little,2006). Prevention Though some vaccines are available for prevention of FELV in the future, none of them guarantee 100% protection. The American Association of Feline Practitioners has classified vaccines into core and non core categories. The core category includes vaccines which are absolutely vital for the cats while the non core vaccines are required only for cats that are more prone to this disease. The vaccines for FeLV are placed in the latter category. Thus, vaccination for FeLV is considered essential for outdoor, wild, felines and also neonates. The most recent vaccine consists of the canarypox virus. This live virus originates in birds but can’t replicate within mammals. (Poulet et al, 2003). It is commercially sold as Purevax FeLV in the USA and Eurifel FELV in the UK. Some of these vaccines have also been shown to have serious side effects. The presence of aluminium content in these vaccines is believed to lead to the development of sarcomas. (Richards et al, 2006) Development of Immune System in Canis Lupus Neonates Canis Lupus, also known by the names of the Grey Wolf and the Timber Wolf, is the largest mammal of the Canidae. It has survived since the ice age and shares a common ancestry with the domesticated dog. The gray wolf is regarded as being of least concern for extinction according to the International Union for the Conservation of Nature and Natural Resources (Mech and Biotani,2006) The grey wolves have a gestation period of nearly 60-65 days, after which the pups are born in groups of 5-6, called as litter. The neonate pups are born deaf, blind and completely dependant on their mother(Smith,2002) For the first two months, the pups live in dens and feed on the mother’s milk and regurgitated food. They, then spend the next six months under their mother’s surveillance. Once they are eight moths old, they attain independence and also start hunting for themselves. Every living organism is characterized by the presence of the Immune System, which defends the body against foreign cells and pathogens, which are capable of causing diseases. The immune system detects various disease causing agents like virus, bacteria, parasites and then produces a defensive reaction against them. The immune system in vertebrates is constituted by various complexes and mechanisms, making it extremely sophisticated. The Grey Wolf neonates are born with innate immunity, which is the first line of defense. Innate immunity is non adaptive i.e. it does not adapt to a certain substance even after repeated exposure; and non-specific i.e. it reacts against every possible pathogen (Albert et al, 2002). In addition to microbes present in the skin, acid present in the stomach and mucus in respiratory tract and chemicals in saliva form the basic constituents of this system. The neonates also receive immunity from their mother in the form of Immunoglobins(Ig’s). The mother’s milk produced just after birth, also known as the colostrum, also provides immunity to the new born (Beardsley et al,1983) For the first ten weeks, the pups; diet consists only of the mother’s milk. After this period, the pups feed on regurgitated or vomited food. They feed on the scraps of bones or meat present in the vomited food. It is also common for these pups to feed on feces. Though it sounds repulsive, this mode of nutrition actually strengthens the immune system in pups. The exposure to several forms of bacteria and protozoa like Salmonella, E.Coli and Campylobactor stimulates the pups’ immune system to evoke a response, thus preparing the pup for any bacterial attacks in the future. This also builds a resistance against intestinal worms (Smith, 2002) The innate immunity is not sufficient to guard the body against the myriad forms of pathogens present in the environment. In addition to this form of immunity, another kind of immunity, Adaptive Immunity has evolved through the ages in vertebrates. While the innate immunity is present since birth, adaptive immunity develops with age and exposure. As against innate immunity, the Adaptive Immunity is more specialized to fight against specific antigens. It recognises specific pathogens and also builds up a memory in case the same pathogen attacks again in the future. If the latter happens, the body mounts a stronger reaction (Pancer & Cooper,2006).The actions of the immune system are mediated through specialized and differentiated cells including lymphocytes, B Cells and T Cells. When a B cell recognises a foreign pathogen, it reacts by producing substances referred to as antibodies. This constitutes Humoral Immunity. This antibody then combines with the antigen(foreign body), forming an antigen-antibody complex. This binding results in deactivation and neutralization of the disease causing agent. The T Cells, on the other hand, operate through Cell Mediated Immunity. When a T Cell identifies an antigen, it sends chemical messengers to phagocytic cells like macrophages which engulf the pathogenic agent, completely destroying it in the process. (Mech & Biotani,2006) Though the development of adaptive immunity begins right after birth, its maturation continues beyond the first year. As the immune system is very fragile in the neonatal pups, they are extremely vulnerable to viral and bacterial infections. These infections are one of the leading causes of mortality in young pups. Canine Parvovirus is one of the most lethal viruses that infects grey wolf pups, the mortality rate being as high as 80%(Carmichael, 2005). It is a DNA virus that affects wolves, foxes and dogs. The virus affects the gastrointestinal tract, leading to chronic vomiting and diarrhea. It also damages the lymphatic system which leads to severe suppression of the immune system. It may also cause cardiac problems in young pups. It is transmitted through the faeces of the infected wolves. Infected wolves demonstrate classical symptoms like vomiting, dehydration after 5-10 days of being infected. Bibliography Albert et al. 2002. Molecular Biology of The Cell. Garland Science. 0-8153-3218-1 Beardsley, et al. 1983 Induction of T-Cell Maturation by a Cloned Line of Thymic (TEPI). Immunology. 6005-6009 Carmichael, L 2005 An annotated historical account of canine parvovirus". J. Vet. Med. B Infect. Dis. Vet. Public Health 52 (7-8): 303–11. Hoover, E, Mullins, J 1991. Feline Leukemia Infections and Diseases. Medline 15;199 Little, S 2006 Feline Leukemia Virus. The Winn Feline Foundation 08736-0805 Mech, K, Biotani, S 2006 IUCN Red List of Threatened Species IUCN. Available http://www.iucnredlist.org/search/details.php/3746/all [30 August 2008] Pancer, Z, Cooper, M. 2006.The Evolution of Adaptive Immunity. Annu Rev Immunol 24: 497–518. Poulet et al 2003 Hoover, E, Mullins, J 1991. Feline Leukemia Infections and Diseases. Medline 15;199 Richards, J et al 2006 The 2006 American Association of Feline Practitioners Feline Vaccine Advisory Panel report. J Am Vet Med Assoc 229 (9): 1405–41 Smith, A 2002 .Is incest common in gray wolf packs? Behavioral Ecology, 8 (4), 384- 391. Read More