Chronic fatigue syndrome in cats

Chronic fatigue syndrome is a recently diagnosed disease in cats, although reported cases are rare due to difficulty in diagnosing cases. Unlike other species, where activity is a part of normal behaviour, CFS is hard to determine clinically in cats.

Outbreaks and sporadic cases of a human disease with an apparent infective onset, currently called Chronic Fatigue Syndrome (CFS) or Myalgic Encephalomyelitis (ME), have been reported on numerous occasions since 1948 (‘Icelandic disease’). The cause(s), diagnosis and treatment of this condition remain controversial. Besides a debilitating fatigue unrestored by rest, common symptoms of CFS include impaired short term memory and concentration, recurrent sore throats, muscle and joint pain, sleep disturbances and adenopathy. During the past decade, substantial evidence has been generated to support the existence of a CFS-like illness among animals. Although Chronic Fatigue Syndrome has never been clinically reported in dogs and cats, an epidemiological study indicates that a remarkable number (97%) of patients with CFS have animal contacts and that 75% of these pets appear sick or abnormal. Two recent articles describe CFS among horses: as with the disease in humans, equine fatigue syndrome is associated with long-term exhaustion, difficult treatment and immune dysfunctions. Little is known about the syndrome in animals and therefore, since it appears that CFS could be a zoonosis, information generated from studies upon animals may be useful to human researches.

Initial epidemiological studies failed to identify a peculiar virus associated with clinical manifestations of chronic fatigue/chronic pain disorders. More recently, several species of toxin-producing staphylococci have been cultured from humans affected by similar conditions. During 1993, in a attempt to verify a possible correlation with a chronic bacterial infection, 15 canine and feline cases out of 117 diagnosed with CFS, were submitted to blood cultures and biochemical studies. The primary purpose of this study was to describe the frequency of certain biochemical and microbiological anomalies that in association with clinical features led to a diagnosis of CFS . Additional objective was to determine how the syndrome was responsive to an arsenical drug, thiacetarsamide sodium (Caparsolate, Abbott Laboratories) given intravenously in low dosage, as previously observed in horses.

Fig.1. Cat with CFS. Micrococci-like organisms can be observed on the external surface of some red blood cells (x100). Fig.2. Staph-positive blood culture from a CFS animal patient. Fig 3. Gram positive cocci (staph-) in a stained smear from a colony on a Columbia plate, after rapid blood culture from a cat with CFS (x100)

Findings of experimental studies

It is notable that symptoms, sero-chemical evidences and microbiological findings observed in 7 dogs and 8 cats diagnosed with CFS are not in contrast with similar characteristics of the syndrome emerging from recent human researches on the topic, meanwhile the striking responsiveness to an arsenical drug do not differ from the results obtained in ancient times against vaguely resembling-CFS veterinary and human conditions. These results apparently support also the zoonotic implications of CFS pointed out by some authors. The data collected shows that representatives of a family of bacteria, Micrococcaceae, and of a genus, Staphylococcus, are to be seen in the blood of such cases. There is not direct proof that they cause the disease, but their presence could no longer be seen in fresh blood smears made 10-30 days after treatment and recovery. In the case of cat #66, blood culture proved Staph-positive before treatment and bacteria-negative 4 months later. All these elements are suggestive of an underlying staphylococcal infection in CFS animal patients. The use of arsenical drugs is today rediscovered against a huge variety of haematological and solid tumours . This may be the key for supporting the approval of these medicaments even against Chronic Fatigue Syndrome.

In summary, this report presents evidence that a clinical CFS-like illness exists in dogs and cats. In comparison with ‘healthy’ and ‘sick with other illness’ control groups the CFS-affected animals showed a significant prevalence (60%) of Staph-positive blood cultures and presence of micrococci in the blood before therapy, with constant and stable disappearance after treatment and clinical recovery. An increased frequency of toxin-producing coagulase-negative staphylococci has been reported also in humans with chronic pain/fatigue complaints. Determining the comparative medical importance of these isolates and of the therapeutic solution produced awaits the results of future studies.