African
Journals Online
Journal of the South African Veterinary Association
Genetic parameters for resistance to Haemonchus
contortus in Merino sheep in South Africa : article
Nieuwoudt, S.W.Theron, H.E.Kruger, L.P. 4-7
Abstract: Resistance to natural infections of Haemonchus
contortus (wireworm) was studied in Merino sheep. From
February 1995 to July 1996 data were collected from the OTK
Merino Stud on the farm Wildebeesfontein near Hendrina in
Mpumalanga province. >From March 1998 to January 2000 another
Merino flock at Irene in Gauteng province was included in the
study. In both cases, 50 randomly-chosen animals from each group
of lambs weaned were sampled weekly for faecal egg count (FEC)
until a mean of 2500 eggs per gram faeces (epg) was reached. At
this stage, all lambs in the group were sampled for FEC, packed
cell volume (PCV) and live mass in the case of the
Wildebeesfontein flock. Animals were monitored from weaning to
about 1 year of age. Data from 5 different groups of lambs (583
animals and 1722 records in total) with genetic links were
accumulated and analysed. Variance components and resulting
heritabilities for logFEC and PCV were estimated using a
bivariate animal model with repeated records. The estimated
heritabilities were 0.24 ± 0.02 for logFEC and 0.14 ± 0.02 for
PCV. A strong negative correlation (–0.84 ± 0.06) existed
between the 2 traits. The genetic correlation between PCV and
live mass for the Wildebeesfontein flock was low (0.28 ±0.09),
while that between logFEC and live mass was negative, although
not significantly different from zero (–0.13 ± 0.09). These
results suggest that FEC can be used as a selection criterion for
resistance to H. contortus infections in Merino sheep.
Clinical and serological response of wild dogs (Lycaon
pictus) to vaccination against canine distemper,
canine parvovirus infection and rabies
Van Heerden, J.Bingham, J.Van Vuuren, M.Burroughs,
R.E.J.Stylianides, E. 8-12
Abstract: Wild dogs Lycaon pictus (n = 8)
were vaccinated 4 times against canine distemper (n = 8)
(initially with inactivated and subsequently with live attenuated
strains of canine distemper) and canine parvovirus infection (n
= 8) over a period of 360 days. Four of the wild dogs were also
vaccinated 3 times against rabies using a live oral vaccine and 4
with an inactivated parenteral vaccine. Commercially-available
canine distemper, canine parvovirus and parenteral rabies
vaccines, intended for use in domestic dogs, were used. None of
the vaccinated dogs showed any untoward clinical signs. The
inactivated canine distemper vaccine did not result in
seroconversion whereas the attenuated live vaccine resulted in
seroconversion in all wild dogs. Presumably protective
concentrations of antibodies to canine distemper virus were
present in all wild dogs for at least 451 days. Canine parvovirus
haemagglutination inhibition titres were present in all wild dogs
prior to the administration of vaccine and protective
concentrations persisted for at least 451 days. Vaccination
against parvovirus infection resulted in a temporary increase in
canine parvovirus haemagglutination inhibition titres in most
dogs. Administration of both inactivated parenteral and live oral
rabies vaccine initially resulted in seroconversion in 7 of 8
dogs. These titres, however, dropped to very low concentrations
within 100 days. Booster administrations resulted in increased
antibody concentrations in all dogs. It was concluded that the
vaccines were safe to use in healthy subadult wild dogs and that
a vaccination protocol in free-ranging wild dogs should at least
incorporate booster vaccinations against rabies 3–6 months
after the first inoculation.
Morphological and histochemical observations of the organic
components of ostrich eggshell : article
Richards, P.D.G.Botha, A.Richards, P.A.
13-22
Abstract: The organic component of the avian eggshell can
be divided into 3 portions, the shell membranes, the matrix and
the cuticle. These have been well characterised in the chicken
but little has been published with regard to the ostrich (Struthio
camelus). A number of recent studies have indicated that the
cause of intra-shell embryonic deaths in the ostrich is similar
to intra-shell embryonic deaths that occur in the chicken. These
deaths in the chicken are associated with the loss of or damage
to the waxy cuticle and other organic components of the eggshell,
which is reported to be absent in the ostrich eggshell. In this
study, preliminary morphological and histochemical analyses, at
the level of the light and electron microscope, have
characterised the various organic components of the ostrich
eggshell. The results of the histochemical and electron
microscopical analyses suggest that there mayonly be 1 shell
membrane in this species, which could play a major role in the
limitation of bacterial penetration to the embryonic chamber. The
shell membrane has a distinct elemental profile as determined by
EDSanalysis. The matrix is shown to decrease in mesh size from
the mammillary layer to the vertical crystal layer. The closer
packing of the mesh may indicate the presence of a
morphologically discernible termination signal to calcification
or the remnants of an evolutionary calcified cuticle. The matrix
of the pores may also forma defensive barrier against bacterial
invasion, which could be damaged as a result of dipping the eggs
before incubation.
A preliminary undifferentiated faecal egg count reduction
test survey in the Caledon area : article
Dreyer, F.H.
23-25
Abstract: During October 1998 a study was performed in the
Caledon area to determine the presence of anthelmintic resistance
in the southern Western Cape, which falls within the winter
rainfall region of South Africa. The study took the form of an
undifferentiated faecal egg count reduction test (FECRt) survey.
The predominant worm genera of the region are Teladorsagia
and Trichostrongylus, but Haemonchus causes
occasional outbreaks in sheep. No resistance data for any area in
the Western Cape Province are available at present. Resistance
(<90 % FECR) was recorded on 73 % of the farms included in the
study, with 46 %of these involving resistance to 1 drench, 36 %
to 2 drenches and 18 % to 3 drenches. No moxidectin resistance
was detected when it was administered at the therapeutic dosage
of 0.2 mg/kg. The results of this study show clearly that
resistance of nematodes to other anthelmintics occurs in the
Caledon area.
Ixodid ticks on indigenous goats owned by small-scale
farmers in four communal grazing areas in South Africa : article
Bryson, N.R.Tice, G.A.Horak, I.G.Stewart, C.G.Du
Plessis, B.J.A.
26-30
Abstract: Indigenous goats belonging to small-scale
farmers in 4 communal grazing areas in South Africa were sampled
for ixodid ticks during the period September 1991 to May 1993.
Three of these areas were in the North West Province (Rietgat,
Madinyane and Bethany), and one in Mpumalanga Province (Geluk).
No tick control was practised unless requested by the owners.
Seven ixodid tick species, of which the majority were immature
ticks, were collected from the goats in North West Province. Amblyomma
hebraeum was the most numerous of these, followed by Rhipicephalus
evertsi evertsi and Rhipicephalus appendiculatus.
Substantially more ticks were collected from goats at Rietgat
than at the Madinyane and Bethany grazing areas. Five tick
species were collected at Geluk and R. evertsi evertsi
comprised more than 95 % of the total population. At Rietgat and
Geluk A. hebraeum nymphs were present on goats throughout
the year, while most R appendiculatus nymphs were
collected during September and October 1991 and most adults
during January and February 1992. At both Rietgat and Geluk most
immature R. evertsi evertsi were collected from spring to
late summer, while adults were present throughout the year.
Possible application of a nematophagous fungus as a
biological control agent of parasitic nematodes on commercial
sheep farms in South Africa : review article
Faedo, M.Krecek, R.C.
31-35
Abstract: Biological control of parasitic nematodes of
livestock is currently under development and represents another
tool that may be integrated into helminth parasite control
strategies. This paper presents a brief introduction to
commercial sheep farming in South Africa and currently available
nematode parasite control methods. These include the FAMACHA®
clinical assay, strategies of pasture management, dilution of
resistant worm species by introduction of susceptible worms,
breed resistant sheep and nutritional supplementation. The
purpose of this paper is to outline the principles of biological
control using nematophagous fungi and how it may be applied on
sheep farms in South Africa.
An epidemiological survey demonstrating decline in
reproductive efficiency with age and non-seasonality of
reproductive parameters in German shepherd bitches in Kenya :
short communication
Mutembei, H.M.Mutiga, E.R.Tsuma, V.T.
36-37
Abstract: An epidemiological survey undertaken in Kenya
indicated that 2 previously well-established factors, namely
decline in reproductive efficiency with age, and non-seasonality
of canine reproductive parameters, hold true for German shepherd
(GSD) bitches in Kenya. Data collection formswere distributed to
randomly selected GSDbreeders and information so obtained was
verified using East African Kennel Club records. Whelping was
recorded throughout the year. The litter size varied from 1 to 14
pups per litter with a mean of 6.3 ±0.4 SD puppies. Records of
567 whelpings and 3592 puppies were studied. The mean monthly
whelping rate was 47.3 ±7.2. There was no significant difference
in the mean litter size by month (P < 0.05).
Neosporosis in a white rhinoceros (Ceratotherium
simum) calf : special report
Williams, J.H.Espie, I.Van Wilpe, E.Matthee, A.
38-43
Abstract: A16-day-old white rhinoceros calf died suddenly
while in excellent condition and showing no obvious previous
clinical signs. It was the 9th calf of a mature female kept
free-ranging with 11 other rhinoceros as well as various other
game species on a 2000 hectare game breeding centre adjacent to
the town of Lichtenburg and outlying cattle farmlands in the
Northern Province. At post mortem examination, death was
ascribed to heart failure. There was marked multifocal to
coalescing subacute parasitic myocarditis with numerous
proto-zoan bradyzoite cysts and free tachyzoites present amongst
the predominantly round cell inflammatory infiltrate. The
coccidian was positively identified as Neospora sp. using
both polyclonal and murine monoclonal Neospora caninum
antibody immunohistochemistry in the avidin-biotin technique. The
parasites stained poorly with Toxoplasma gondii-specific
immunoperoxidase staining. Ultrastructurally, a section of a
bradyzoite-containing cyst, as well as tachyzoites, were largely
but not totally consistent with those described for Neospora
caninum. The dam showed no sign of illness. Neosporosis
affecting white rhinoceros (Ceratotherium simum) has not
previously been reported. A summarised overview of neosporosis
from selected publications and a recent review is given.
Cytomegalovirus infection in a pig in South Africa : case
report
Collett, M.G.Roberts, D.C. 44-46
Abstract: An 8-week-old piglet with dyspnoea, bilateral
mucopurulent nasal discharge and mouth breathing was euthanased
and a necropsy was performed. Apart from histological evidence of
diffuse rhinitis, large intranuclear inclusion bodies,
pathognomonic for porcine cytomegalovirus infection, were
detected within mucous glands on the nasal turbinates. This is
the first such case to be diagnosed in South Africa.
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