6 May 2000 

CHRONIC FATIGUE SYNDROME IN HORSES: DIAGNOSIS AND TREATMENT OF 4 CASES

COMPARATIVE IMMUNOLOGY, MICROBIOLOGY & INFECTIOUS DISEASES
(2000) Volume 23 n.4

AUTHOR:
Walter Tarello, veterinary surgeon
C.P. 42, I - 06061 Castiglione del Lago
PERUGIA (Italy)
e-mail: tarello@iol.it 11

Abstract:
A report from England has suggested that Chronic Fatigue Syndrome exists
in equines and constitutes an emerging veterinary problem. Preliminary
epidemiological studies seem to confirm the zoonotic implications of CFS.

An arsenical drug, thiacetarsamide sodium, was administered to four
horses with a diagnosis of Chronic Fatigue Syndrome (CFS), already
treated unsuccessfully with different medications. The CFS-like lethargy,
with accompanying symptoms and signs, of the four animals obtained a
complete remission after intravenous treatment with this drug at low
dosage (0.1 mg/Kg/day). No adverse side effects were ever noticed. This
clinical response was associated with recovery from anaemia and decrease
of muscular enzyme values in two of the four horses. In all patients,
micrococci-like bacteria found before treatment adhering to the outer
surface of many red blood cells, disappeared at post-treatment controls.
Considerations are made on the possible action of an arsenical drug, used
isolately, in the treatment of CFS.

Introduction:
A human illness characterized by prolonged, debilitating fatigue and
cognitive complaints, was called at first "Icelandic disease"(1948),
"post-polio syndrome" or "myalgic encephalomyelitis", and has been
anecdotically related to similar syndromes in animals. It is nowadays
known as "Chronic Fatigue Syndrome" (CFS) or "Chronic Fatigue and Immune
Dysfunction Syndrome" (CFIDS), with many papers about it being published
every year in journals of human medicine [7, 22, 23, 25, 38, 40].

Its chief symptom, fatigue, can be combined with many others, such as
headache, fever, sore throats, lack of concentration, failing short-term
memory, muscle and joint pains, insomnia, increased allergic reactions [4,
30] .

Recent magnetic resonance studies, showing specific damage of certain
areas of the brain, have documented the really organic nature of the
disease [21, 29, 36 ].

Immune abnormalities are also observed frequently in CFS patients [16, 30,
50], such as the reduction in the number and activity of the NK cells, a
low CD4/CD8 ratio, and, in some cases, a fall in the absolute number of
CD4 lymphocytes ("Idiopatic CD4 lymphocytopenia"). These abnormalities
make the disease a true acquired immune deficiency syndrome.

Neurological disorders (episodic weakness, seizures and lethargy) are of
common observation in veterinary medicine, but there are very few reports
and epidemiologicals studies on CFS-like illnesses in animals. First in
1974, Kronevi & al. [20], in Sweden, reported a similar condition in a
group of cats with muscular weakness, neurological symptoms ("staggering
disease") and

leukopenia. Treatment with anti-microbial drugs and corticosteroids was
unsuccessful and most cats deteriorated, died, or had to be put to sleep
after several months. Researchers in Sweden and Germany have recently
carried out intensive studies on this non-suppurative
meningoencephalomyelitis, and the findings have been those of a pronounced
inflammatory reaction of the central nervous system [24].

Cheney published, on The CFIDS Chronicle of Spring 1991, the first
informal study on the correlation of CFS in humans and their pets,
reporting a 50% of unusually severe illness, even with sudden deaths,
among pets owned by subjects suffering from CFS . None of the controls
(animals in contact with people not affected by CFS) showed any of the
neurological disorders ( seizures, weakness of limbs and unsteadiness)
exhibited by the diseased animals. Following Cheney’s studies,
Breitschwerdt & al. [6] reported canine cases of episodic weakness
associated with lactic acidosis from exertion and myopathy, and pointed
out the number of similarities between this condition and human
mitochondrial myopathies. The size and shape of mitochondria have been
found to be abnormal in up to 75% of patients [3]; these features ,
however, are shared with other syndromes.

Human herpersviruses (HHVs) have been considered as a possible cause of
CFS since the early ‘80’s. Similarly, in the ‘90’s, equine herpesviruses
(EHV-1, EHV-4) have been thought to be the cause of myopathies in horses.
It is known nowadays that HHV-6, HHV-7, Epstein-Barr virus and
Cytomegalovirus are not implicated in the etiology of CFS in human
subjects [49]; and, that elevated levels of antibodies against several
viral agents indirectly reflect the degree of immune system suppression in
some CFS patients, without showing a direct causal relationship [4].

In 1992, circulating enterovirus antigens and leukopenia were
respectively found in 79% and 88% of 32 horses with persistent, marked
lethargy, stationed in Newmarket, UK. The condition was called "Equine
Fatigue Syndrome" by Ricketts & al. [32]. These authors found similarities
between the conditions affecting the two species, and pointed out that a
certain number of human patients with CFS suffer from persistent
enterovirus infection. Long-term rest was adopted, with controversial
results, as treatment for these cases.

Similar equine cases were observed, in the same year, in this writer’s
veterinary practice. It was remembered that, until recently, some
arsenical preparations had been used in CFS-like veterinary conditions,
including ‘asthenia in horses’ and ‘general debility’[48]: for instance,
arsonoacetic acid as ‘general stimulant in nervous diseases’, sodium
arsenate in rheumatism; arsenic acid solution in blood diseases and
arsenoacetic acid (Tonarsan) as ‘injectable tonic for horses’. With the
advent of modern antibiotics and chemotherapy, arsenical drugs fell into
disuse in both human and veterinary medicine (respectively, in the ‘50’s
and in the ‘70’s).

The purpose of this paper is to report the author’s personal experience,
that arsenical drugs can still be useful - at least in veterinary practice
- in inducing complete remission of a CFS-like equine disease. The four
cases described here were resistant to conventional chemotherapy and
shared common hematological abnormalities, including the unexpected
presence of micrococci-like bacteria scattered on the outer surface of red
blood cells.

The complete article is at:
http://www.geocities.com/cfsinhorses