COCCIDIOSIS OF CALVES (BLOODY DIARRHOEA)
Guillebeau
(1893) observed two types of parasites: a large egg-shaped variety and a small
spherical one. He found that
multiplication occurred in both the small and large intestine and that the
developmental stages of the parasite could be observed in the epithelial
cells. Züblin (1908) reported the
development of four sporocysts in each oöcyst; each sporocysts producing two
sporozoites; he noted rounded oöcysts and larger egg-shaped forms, and named
these organisms, which he apparently regarded as morphological types of the
same coccidium, Eimeria bovis. Similar parasites were described as the
cause of enteritis in calves in South Africa by Jowett (1911), and in East
Africa by Montgomery (1910).
Photomicrographs
of oöcysts of bovine coccidia.
Final
magnification, 1,000 times.
1. Eimeria subspherica
6. E. cylindrica
2. E. zurnii, spherical
type 7. E. bovis
3. E. zurnii, elliptical
type 8. E. Condenses
4. E. alabamensis
9. E. bukidonensis
5. E. elipsoidalis 10. E. auburnensis
THRICHOMONIASIS
Robinson (1937)
was the first to record the presence of bovine trichomoniasis in South Africa,
but the disease has not yet assumed serious proportions; at most, isolated
cases have been reported. In 1941 the
writer also studied a single case of trichomonad infection in a Friesland
heifer that had aborted a four-months-old foetus. The source of the infection could be traced and no further cases
occurred.
DOURINE
The first
official record of dourine in South Africa was in July, 1914, when Lyons
reported the disease in Griqualand West, but transmission experiments carried out
at Onderstepoort with blood from affected mares were all reported as
negative. During the same year the
malady was observed in South-West Africa (Maag, 1919), and it was believed that
the infection had been introduced by means of a stallion imported from
Hungary. But according to information
obtained by Schulz (1935) from farmers, slapsiekte was observed in the Herbert
District in 1906, the year in which an outbreak occurred in East Prussia;
according to Walker (1918), however, the disease was first observed by a farmer
in 1911. Schulz believes that the
infection was introduced into the Union either by means of donkey jacks
imported from Canada, or by means of transport horses that were returning from
South-West Africa during the Herero Campaign.
In 1916, Andrews
(Walker, 1918) made a number of observations on the nature of the disease, and
noticed that it occurred in an atypical form resembling the modified form
described in Canada, and that exposure to unfavorable environmental conditions
generally precipitated the symptoms in equines affected with the latent form;
only breeding animals were found to be affected; swelling of the vulvar lips
but plaques were not observed. The
investigations commenced by the disease either to horses or to laboratory
animals – rabbits, guinea-pigs, rats and mice – but he succeeded in finding
trypanosomes in a puppy six days after it had been injected with blood from an
affected mare. Walker submitted sera
from a number of diseased mares to Watson of Canada, for the complement
fixation test, and positive results were obtained with a number of the examples
submitted. Sera of some of the mares
inoculated with blood from affected equines also yielded positive results,
which showed that Walker’s transmission experiments were positive.
All attempts to
demonstrate Trypanosoma equiperdum in
the blood and tissues of affected equines failed until van Rensburg (Parkin,
1947) showed that parasites could be readily obtained from the vaginal washings
of affected mares and from the blood by means of a method of sedimentation and
centrifulatization.
AFRICAN HORSE SICKNESS (PERDESIEKTE)
Historical. -
Horsesickness has been known in South Africa for many centuries, and the
first cases of the disease were observed probably soon after the occupation of
the Cape of Good Hope by the Dutch East India Company.
According to
Moule (1896) the first historical references to a disease that can be regarded
as horsesickness are found in an Arabian document “Le Kitab El-Akoua El-Kafiah
Wa El Chafiah.” An outbreak of the
scourge was recorded in the year 728 of the Hegira (A.D. 1327-8). Another very early reference to a disease in
Africa, which can be identified as horsesickness, was made by Fater Monclaro in
his account of the journey of Francisco Barreto to East Africa in 1569 (Theal,
1899). A description was given of a
fatal disease that affected horses imported from India into East Africa
(Sena). One of the animals, a stallion,
on being led, was noticed to fall and cast up a yellow material. Death was attributed to the malicious
poisoning of the grass by natives. It
is quite possible that the yellow material brought up by the stallion was a
serous fluid or froth escaping from the nose, a condition commonly noticed in
horsesickness.
All the
available information clearly shows that the virus of horsesickness existed in
the Cape in some indigenous animals, which acted as reservoir hosts, when the
first settlers arrived. No indigenous
horses existed in the country, and the disease soon made its appearance when
horses were imported from Europe and the East Indies where horsesickness was
not known.
According to
Theiler (1921) frequent reference was made to the disease in the records of the
Dutch East India Company. As early as
1719 nearly 1,700 horses succumbed to the dreaded “perreziekte” or
“pardeziekte” in the Cape of Good Hope, and the beneficial effect of frost, in
arresting an outbreak, was already recognized.
Although losses probably occurred every year, particularly severe epizootics
were recorded during the years 1780, 1801, 1839, 1845, 1862, 1891 and
subsequently. The outbreak of 1854-5
was considered to be the most virulent on record. The mortalities for that year amounted to nearly 70,000,
comprising more than 40 per cent of the entire horse population of the Cape of
Good Hope at the time. The scourge
first appeared in the eastern Province and swept westwards as far as the
mountains of Clanwilliam, affecting all parts except the Cape Peninsula. According to the rainfall records for that
year, kept at Grahamstown, the precipitation was abnormally high just before
the outbreak occurred. From the time
that rainfall records have been available there has been definite proof that
every severe outbreak of horsesickness was preceded by an exceptionally heavy
rainfall.
During the 19th
century several travelers, hunters, explorers and missionaries encountered
horsesickness in the interior of southern Africa. In the early part of the century, Barrow (1806), Lichtenstein
(1806), and Commissioner de Mist, all referred to the prevalence of
horsesickness in the interior parts of Southern Africa. Later the Voortrekkers suffered severe
losses through horsesickness. Gordon
Cumming (1850) and other hunters reported horsesickness amongst their
horses. Livingstone (1857) was unable
to keep horses and was forced to travel on foot or on the back of an ox.
During recent
years the most severe outbreaks of horsesickness occurred in 1913-14, 1918 and
in 1923. The 1923 epizootic was considered
unprecedented; one farmer in the Prieska area lost 53 out of his 57 horses,
while another lost 250 animals out of a group of nearly 400. In places like Johannesburg and Belfast,
where the disease is not very prevalent, the severity of the epizootic broke
all previous records. Even donkeys
succumbed to the scourge in some parts of the country. The inter-relation between the rainfall and
horsesickness was shown to a striking degree during this outbreak. The heaviest mortalities occurred during
March and April and the disease suddenly stopped soon after the first frost (du
Toit, 1924).
At first
horsesickness was confused with diseases like anthrax, human malaria, and
biliary fever. In Natal, Lambert (1881)
and in South-West Africa, Sander (1895) (Quoted by Knuth and du Toit (1921))
mistook it for anthrax, while Nunn (1888), Rickmann (1895, 1900), and Kuhn
(1911) regarded it as a disease related to malaria of man. Edington (1900, 1904) on the other hand,
propounded various theories about its etiology; at one time he considered the
causal agent to be a fungus, whereas later he confused horsesickness with
equine piroplasmosis and with heartwater.
It was left to M’Fadyean (1900), Theiler (1901), Nocard (1901) and
Sieber (1911) to prove the filterability of the virus of African horsesickness.
Historical. How long blue-tongue has been prevalent in
South Africa is not definitely known, but the disease is considered to be
endemic to South Africa and has probably existed as long as sheep farming has
been carried on. In the Report of the
Cattle and sheep Diseases Commission for 1876 it is stated: “For many years, if not from the time of the
introduction of the Merino sheep into the Colony, there has been prevalent
amongst the flocks a disease known as fever. This disease is most prevalent during the
summer months, and is very much worse in wet seasons.” In the same report it is stated that fat
sheep are more susceptible to fever,
and that the disease is more prevalent in low-lying pastures, valleys, and
kloofs than on high-lying veld. Sheep
that are kept in sheds during summer nights are reported to escape
infection. The morbidity was considered
to be over 30 per cent, and the mortality was stated to be over 90 per
cent. The most important symptoms
described were soreness of the mouth and the feet, and the condition was
compared with foot and mouth disease.
Blue-tongue was
first mentioned by Hutcheon in 1881, when he referred to it as “Fever or Epizootic
Catarrh” in sheep, and in 1893 he described the disease in detail. Spreull (1902, 1905) was the first to make a
detailed study of the malady, and recommended a method of immunization by the
simultaneous inoculation of immune serum and virulent blood. Theiler (1906, 1908) was unable to confirm
Spreull’s observations, but he introduced a method of immunization by means of
virus attenuated by passage for several generations through sheep.
Since 1907
Theiler’s attenuated virus has been used extensively for the prophylactic
vaccination of sheep, and up to 1943 more than 50 million doses of this vaccine
were issued by the Government laboratories at Onderstepoort (Neitz and
Riemerschmid, 1944).
Bluetongue. (Edema of lips and discharge from
nose). (Onderstepoort collection).