1997 Onderstepoort Journal of Veterinary Research, Volume 64, 1997

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Contentes Pages: Onderstepoort Journal of Veterinary Research, Vol ??, 19??

CONTENTS

*Volume 64: Number 1*

Acquisition of protective immunity in Geochelone pardalis against Amblyomma marmoreum (Acari: Ixodidae) nymphal ticks	Tembo, SD & Kiwanuka, A	1

A checklist of helminths from the respiratory system and gastrointestinal tracts of African Anatidae	Alexander, SJ & McLaughlin, JD	5

Failure to establish chronic infection of the reproductive tract of the male horse with a South African asinine strain of equine arteritis virus (EAV)	Paweska, JT	17

Ulcerative pododermatitis in free-ranging African elephant (Loxodonta africana) in the Kruger National Park	Keet, DF, Grobler, DG, Raath, JP, Gouws, J, Carstens, J & Nesbit, JW	25

Camallanus polypteri n. sp. (Nematoda: Camallanidae) in freshwater fishes from Burkina Faso	Kabre, GB & Petter, AJ	33

Aspects of rabies epidemiology in Tsumkwe District, Namibia	Laurenson, K, Esterhuysen, J, Stander, P & Van Heerden, J	39

A scanning electron-microscope examination of the scolex of Houttuynia struthionis	Fourie, HJ, Van Amelsfoort, AF, Michael, LM & Putterill, JF	47

In vitro cultivation of Babesia equi: detection of carrier animals and isolation of parasites	Zweygarth, E, Just, MC & De Waal, DT	51

Effects of growth conditions and incubation times on the expression of antigens of Haemophilus paragallinarum which are detected by monoclonal antibodies	Verschoor, JA, Bragg, RR & Coetzee, L	57

Schistosoma mattheei infection in cattle: the course of the intestinal syndrome, and an estimate of the lethal dose of cercariae	Van Wyk, JA, Van Rensburg, LJ & Heitmann, LP	65

Research communications:

Canine visceral leishmaniosis: first case in Zambia	Matsukawa, K, Chiti, L, Yoshima, M & Sayer, PD	77

Discovery of a Culicoides imicola-free zone in South Africa: preliminary notes and potential significance	Meiswinkel, R	81

Book review:

Preventing the spread of aquatic animal diseases		87

Guide for authors		89


*Volume 64: Number 2*

Obituary: Dr Max Sterne	Verwoerd, DW

Antibodies against some viruses of domestic animals in southern African wild animals	Barnard, BJH	95

Pathological changes in calves that died from experimental water intoxication	Njoroge, EM, Maribei, JM & Mbugua, PN	111

Acceptance of candidate baits by domestic dogs for delivery of oral rabies vaccines	Linhart, SB, Baer, GM, Balderas Torres, JM, Engeman, RM, Collins, EF, Meslin, FX, Schumacher, CL, El-Taweel, AH & Wlodkowski, JC	115

Helminth fauna of Anas undulata, Anas erythrorhyncha, Anas capensis and Anas smithii at Barberspan, South Africa	Alexander, S & McLaughlin, JD	125

Assessment of bovine hoof conformation and its association with lameness, animal factors and management practices on small-scale dairy farms in Kiambu district, Kenya	Gitau, T, Mbiuki, SM & McDermott, JJ	135

Prevalence of equine piroplasmosis in Central Mongolia	Avarzed, A, De Waal, DT, Igarashi, I, Saito, A, Oyamada, T, Toyoda, Y & Suzuki, N	141

Effect of the South African asinine-94 strain of equine arteritis virus (EAV) in pregnant donkey mares and duration of maternal immunity in foals	Paweska, JT	147

Development of the OPgun for bombardment of animal tissues	Brayton, KA, Bothma, GC, Vogel, SW & Allsopp, BA	153

Research communications:

Cryopreservation of sheathed third-stage larvae of Oesophagostomum radiatum (nodular worm of cattle)	Titoy, GAP, Van Rensburg, LJ & Van Strijp, MF	157

Cryopreservation of third-stage larvae of Strongylus vulgaris (large strongyle of horses)	Titoy, GAP & Van Rensburg, LJ	159


*Volume 64: Number 3*

A comparison of the helminth communities in Anas undulata, Anas erythrorhyncha, Anas capensis and Anas smithii at Barberspan, South Africa	Alexander, SJ & McLaughlin, JD	161

Escherichia coli serotypes in pigs in South Africa	Henton, MM & Engelbrecht, MM	175

Krimpsiekte, associated with thalamic lesions, induced by the neurotoxic cardiac glycoside, cotyledoside, isolated from Tylecodon wallichii (Harv.) Toelken subsp. wallichii	Vleggaar, R, Botha, CJ, Van der Lugt, JJ, Erasmus, GL, Kellerman, TS & Schultz, RA	189

Strains of Actinobacillus spp. from diseases of animals and ostriches in Zimbabwe	Mohan, K, Muvavarirwa, P & Pawandiwa, A	195

The binding potential of commercial antibody conjugates with sera of various small terrestrial mammals	Pretorius, A, Oelofsen, MJ, Smith, MS & Van der Ryst, E	201

The humoral immune response in cattle after immunization with a multivalent IBR/PI 3/ Pasteurella haemolytica A1 leukotoxin vaccine	Odendaal, MW, Morris, S, Du Preez, E & Aitchison, H	205

Experimental infection of vaccinated slaughter ostriches with virulent Newcastle disease virus	Verwoerd, DW, Gerdes, GH, Olivier, A & Williams, R	213

Parafilariosis in African buffaloes (Syncerus caffer)	Boomker, JDF, Keet, DF, Kriek, NPJ, Zakrisson, G & Meltzer, DGA	217

Some factors governing the entry of Culicoides spp. (Diptera: Ceratopogonidae) into stables	Barnard, BJH	227

Detection of AHV-1 DNA in lung sections from blue wildebeest (Connochaetes taurinus) calves by in situ hybridization	Michel, AL, Van der Lugt, JJ, Bengis, RG & De Vos, V	235

Research communications:

The endocrine pancreas of the Cape fur seal, Arctocephalus pusillus (Schreber, 1776): an immunocytochemical study	Erasmus, CP & Van Aswegen, G	239

Sparganosis in non-human primates	Chai, D, Farah, I & Muchemi, G	243


*Volume 64: Number 4*

Comparison of ELISA and HI for detection of antibodies against Wesselsbron disease virus	Williams, R, Schoeman, M, Van Wyk, A, Roos, K & Josemans, EJ	245

The control of Glossina morsitans morsitans (Diptera: Glossinidae) in a settled area in Petauke District (Eastern Province, Zambia) using odour-baited targets	Van den Bossche, P	251

Seasonal abundance and parity of stock-associated Culicoides species (Diptera: Ceratopogonidae) in different climatic regions in southern Africa in relation to their viral vector potential	Venter, GJ, Nevill, EM & Van der Linde, TC De K	259

Predation of livestock ticks by chickens as a tick-control method in a resource-poor urban environment	Dreyer, K, Fourie, LJ & Kok, DJ	273

Salmonella isolated from crocodiles and other reptiles during the period 1985-1994 in South Africa	Huchzermeyer, FW, Van der Walt, ML & Steyn, HC	277

Parasites of South African wildlife. XV. Helminths of scrub hares, Lepus saxatilis in the Kruger National Park	Boomker, JDF, Horak, IG & Booyse, DG	285

The structure of the interstitial tissue of the active and resting avian testis	Aire, TA	291

Toxorhynchites-fluorescent antibody system for the detection of bluetongue virus from Culicoides midges (Diptera: Ceratopogonidae)	Habibur Rahman, A & Manickam, R	301

Research communications:

Evaluation of a 3 ml heartwater (cowdriosis) infective blood vaccine dose	Combrink, MP, De Waal, DT & Troskie, PC	309

Seroepidemiological survey of sympatric domestic and wild dogs (Lycaon pictus) in Tsumkwe District, north-eastern Namibia	Laurenson, K, Van Heerden, J, Stander, P & Van Vuuren, MJ	313

Morphological evidence for infection of impala, Aepyceros melampus, platelets by a rickettsia-like organism	Du Plessis, L, Reyers, F & Stevens, K	317

Authors' note: Furunculosis in rainbow trout (Salmo gairdneri) raised in sea water	Boomker, JDF, Huchzermeyer, FW, Henton, MM & Naude, TW	319

Book reviews		321

Author index		327

Subject index		335

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Now showing 1 - 20 of 52

Obituary: Dr Max Sterne
(Published by the Agricultural Research Council, Onderstepoort Veterinary Institute, 1997) Verwoerd, Daniel Wynand; Verwoerd, Daniel Wynand
This volume of the journal is dedicated to Max Sterne in recognition of his contributions to veterinary bacteriology.
Cryopreservation of third-stage larvae of Strongylus vulgaris (large strongyle of horses)
(Published by the Agricultural Research Council, Onderstepoort Veterinary Institute, 1997) Titoy, G.A.P.; Van Rensburg, L.J.; Verwoerd, Daniel Wynand
A technique for the cryopreservation of third-stage larvae of Strongylus vulgaris is described. Infective larvae of S. vulgaris were exsheathed in a 0,16% sodium hypochlorite solution and then transferred into cryotubes containing 0,09% saline. The samples were stored in the gas phase of liquid nitrogen.
Cryopreservation of sheathed third-stage larvae of Oesophagostomum radiatum (nodular worm of cattle)
(Published by the Agricultural Research Council, Onderstepoort Veterinary Institute, 1997) Titoy, G.A.P.; Van Rensburg, L.J.; Van Strijp, M.F.; Verwoerd, Daniel Wynand
Sheathed infective larvae of Oesophagostomum radiatum were successfully cryopreserved by the use of a procedure developed for hookworms. The survival rate, as assessed by motility, was 57,9% after 42 d of cryopreservation.
Development of the OPgun™ for bombardment of animal tissues
(Published by the Agricultural Research Council, Onderstepoort Veterinary Institute, 1997) Brayton, Kelly A.; Bothma, G.C.; Vogel, S.W.; Allsopp, B.A.; Verwoerd, Daniel Wynand
A simple and inexpensive particle-bombardment device, the OPgun™, was constructed for the delivery of DNA into animal tissues. This device is based on the particle-inflow gun first described for plant-cell transfection. The delivery of tungsten particles into the epidermis of the mouse ear, without the use of vacuum and without causing damage to the tissue, was demonstrated. The system was also shown to be capable of inducing antibodies to a foreign gene in mice.
Effect of the South African asinine-94 strain of equine arteritis virus (EAV) in pregnant donkey mares and duration of maternal immunity in foals
(Published by the Agricultural Research Council, Onderstepoort Veterinary Institute, 1997) Paweska, Janusz Tadeusz; Verwoerd, Daniel Wynand
Clinical, virological and serological responses were investigated in five pregnant donkey mares after experimental exposure to the South African asinine-94 strain of equine arteritis virus (EAV), and the duration of maternal immunity to EAV was studied in their foals. In four intranasally inoculated mares, fever with maximum rectal temperatures of 39,1-40,7°C was recorded 2-11 d after challenge. All the inoculated mares developed mild depression, and a serous ocular and nasal discharge; in three mares mild conjunctivitis was observed. The virus was recovered from the nasopharynx and from buffy-coat samples of all the mares 3-10 d, and 2-16 d post inoculation (p.i.), respectively. Seroconversion to EAV was detected on days 8- 10 p.i. Peak serum-virus- neutralizing antibody titres of log₁₀1,8-2,4, and lgG ELISA OD values of 0,85-2,15 were recorded 2-3 weeks p.i. The in-contact (p.c.) control mare developed fever on days 15-19 post exposure, and showed mild clinical signs of equine viral arteritis similar to those observed in the inoculated mares. Seroconversion to EAV was detected in the p.c. mare on day 20 post exposure, and virus was isolated from nasal swabs and blood samples collected at the time of the febrile response and 1-3 d afterwards. None of the mares aborted. After they had given normal birth 45-128 d p.i. or after p.c. exposure, no virus could be isolated from their placentas. The concentration of EAV-neutralizing antibody in colostrum was two to eight times higher than in serum samples collected at the time of parturition. All the foals born to infected mares were clinically normal at the time of birth and throughout the subsequent 1-2 months of observation. No EAV was recovered from the bully-coat fraction of blood samples collected at birth nor from those collected on days 1, 2 and 7 after birth. Also, no virus-serum- neutralizing or lgG ELISA antibody to EAV was detected in sera collected immediately after birth before the foals started nursing. The colostrum-derived maternal antibodies against EAV gradually declined and could not be detected by either the VN test or ELISA for 2-3 months after birth. This study demonstrates that the asinine-94 strain of EAV does not cause abortion in pregnant donkey mares. Furthermore, no carrier state could be demonstrated in foals born to mares infected at the time of pregnancy.
Prevalence of equine piroplasmosis in Central Mongolia
(Published by the Agricultural Research Council, Onderstepoort Veterinary Institute, 1997) Avarzed, A.; De Waal, D.T.; Igarashi, I.; Saito, A.; Oyamada, T.; Toyoda, Y.; Suzuki, N.; Verwoerd, Daniel Wynand
Antigen for the indirect fluorescent antibody test (IFAT) was routinely prepared from infected erythrocytes from horses experimentally infected with Babesia equi and Babesia caballi. With the successful establishment of in vitro cultures of B. equi and B. caballi, it is now possible to employ culture- derived antigens in this test. In this study, in vitro-propagated B. equi- and B. caballi-infected erythrocytes were used as antigen in the IFAT. Various modifications to an established protocol had to be implemented to allow repeatable results. Cultures with 3-4% parasitized erythrocytes were found to be most suitable. As cross-reactions of control sera on heterologous antigen were observed at serum dilutions of up to 1/40, a reciprocal titre of 80 was considered to be positive. In positive samples, specific fluorescence of Babesia parasites and/or erythrocyte membranes was observed. Fifteen sera from Babesia-free horses from Japan all tested negative in the IFAT. One hundred and ten field-horse sera from Central Mongolia were investigated in this study. The results indicate that both B. equi and B. caballi are endemic in horses in Central Mongolia, with 88,2% and 84,5% of horses being seropositive to B. equi and B. caballi, respectively.
Assessment of bovine hoof conformation and its association with lameness, animal factors and management practices on small-scale dairy farms in Kiambu district, Kenya
(Published by the Agricultural Research Council, Onderstepoort Veterinary Institute, 1997) Gitau, T.; Mbiuki, S.M.; McDermott, J.J.; Verwoerd, Daniel Wynand
Digital health and conformation were assessed in 216 dairy cattle on 78 randomly selected small-scale farms. For each cow, gait was assessed and the digits examined in detail. Hoof measurements (angle and length of the dorsal hoof wall, heel depth and hoof-base area) were also made. Hoof measurements varied most between individual cattle. Dorsal angle was correlated with heel depth (r = 0,53; P = 0,001) and dorsal length (r = -0,40; P = 0,001). The hoof-base area was correlated with the dorsal length (r = 0,41; P = 0,001). There were significant breed differences in dorsal angle (P = 0,03) and dorsal length (P < 0,01). The dorsal angle was correlated with parity and body condition, while the dorsal length, heel depth and the hoof-base area were correlated with the heart girth (P< 0,01). Hoof conformation was associated with both clinical lameness and hoof lesions. A 1cm increase in the dorsal length increased the odds of lameness by 16,9, heel erosion by 1,8, underrunning by 5,4 and overgrowth by 40 (P < 0,01).
Helminth fauna of Anas undulata, Anas erythrorhyncha, Anas capensis and Anas smithii at Barberspan, South Africa
(Published by the Agricultural Research Council, Onderstepoort Veterinary Institute, 1997) Alexander, S.; McLaughlin, J.D.; Verwoerd, Daniel Wynand
Thirty-four species of gastrointestinal helminths were found in 25 Anas undulata, 21 Anas erythrorhyncha, ten Anas capensis and seven Anas smithii collected at Barberspan, South Africa. Excluding four new taxa, 11 new African records, and 14, 11, 12 and nine new host records were established for Anas undulata, Anas erythrorhyncha, Anas capensis and Anas smithii, respectively. The helminth community included 13 cosmopolitan species, seven species known only from the holarctic, one species known only from the south Pacific and 13 new or unidentified species that appear to be restricted to Africa. The infection levels of the common helminth species in the mainly carnivorous Anas capensis and Anas smithii, were generally much higher than those of species infecting Anas undulata or Anas erythrorhyncha.
Acceptance of candidate baits by domestic dogs for delivery of oral rabies vaccines
(Published by the Agricultural Research Council, Onderstepoort Veterinary Institute, 1997) Linhart, S.B.; Baer, G.M.; Balderas Torres, J.M.; Engeman, R.M.; Collins, E.F.; Meslin, F.X.; Schumacher, C.L.; El-Taweel, A.H.; Wlodkowski, J.C.; Verwoerd, Daniel Wynand
Protocols for evaluating oral rabies vaccine baits for domestic dogs were field tested in central Mexico, after which dog-food manufacturers and suppliers to the pet-food industry were advised as to potential ingredients for use in prototype dog baits. Bait-preference trials in which confined dogs were used were then undertaken, followed by field tests of free-ranging farmer-owned dogs in three towns in the Nile River Delta region of Egypt. Both confined and free-ranging dogs showed strong preferences for certain baits or bait coatings (poultry, beef tallow, cheese, egg and a proprietary product). Fish-meal polymer baits, widely used for wildlife species, were less preferred. In Egypt, a commercial dog-food-meal bait coated with beef tallow and dry cheese was consumed at a rate approaching that of a chicken-head bait. The percentage baits that were actually eaten after they had been offered to dogs, ranged from 71-96% for household dogs tested in Mexico, 65-91% for confined dogs (beagles and mixed breeds) tested in the United States, and 32-88% for farmer-owned dogs tested in Egypt.
Escherichia coli serotypes in pigs in South Africa
(Published by the Agricultural Research Council, Onderstepoort Veterinary Institute, 1997) Henton, Marijke M.; Engelbrecht, M.M.; Verwoerd, Daniel Wynand
This retrospective study was based on 674 cases of colibacillosis in pigs submitted to the diagnostic bacteriology laboratory of the Onderstepoort Veterinary Institute (OVI) over the 20-year period ranging from 1971-1991. During this time, 28 840 cases from various livestock species were received, of which 4 162 (14,4%) were from pigs. The 674 porcine cases selected for this study were included if an E. coli infection had been suspected by the referring veterinarian, and typable E. coli strains were then isolated by this laboratory. Enteritis (45,5%) and septicaemia (46 ,9%) were the most common syndromes, with agalactiae (1,4 %) and abortion (1,1 %) representing a far lower prevalence. Oedema-disease signs were described by the submitting veterinarian in only 12 cases. Samples were received from weaners and sucklers in relatively equal numbers until 1981, but subsequently samples from sucklers declined, while those from weaners remained high. There were 69 different somatic and capsulated (OK) antigen groups associated with E. coli infections in pigs. Escherichia coli O149 was the most common isolate (45,8%), while E. coli O141 was the next most common isolate (18,3%) . This was followed by O9 (8,9%), O20 (5,2%) and O8 (3,1%). All other serotypes together accounted for less than 20 % of the total number of cases, and were isolated fewer than 20 times each. The fimbrial attachment factor, F4 (K88) was found associated with 46,9% of isolates.
Morphological evidence for infection of impala, Aepyceros melampus, platelets by a rickettsia-like organism
(Published by the Agricultural Research Council, Onderstepoort Veterinary Institute, 1997) Reyers, Fred; Stevens, K.; Verwoerd, Daniel Wynand; Du Plessis, Lizette
Ultrastructural studies revealed the presence of a parasite, believed to be Ehrlichia platys, in the blood platelets of impala. At the time of blood sampling all the animals appeared healthy. This is the first report on the presence of this rickettsia in these animals, previously described in canine platelets.
Canine visceral leishmaniosis: first case in Zambia
(Published by the Agricultural Research Council, Onderstepoort Veterinary Institute, 1997) Matsukawa, K.; Chiti, L.; Yoshima, M.; Sayer, P.D.; Verwoerd, Daniel Wynand
Visceral leishmaniosis was discovered in a male 12- year-old Australian cattle dog in September 1994. Canine leishmaniosis has not previously been reported in Zambia.
Discovery of a Culicoides imicola-free zone in South Africa: preliminary notes and potential significance
(Published by the Agricultural Research Council, Onderstepoort Veterinary Institute, 1997) Meiswinkel, R.; Verwoerd, Daniel Wynand
In December 1993, a light-trap survey was made of the Culicoides found at eight horse stables and dairies in the sandy dune field west of Port Elizabeth, South Africa. While it was notable that Culicoides numbers were low (4 749) and that the diversity was poor (15 species) , the most remarkable fact to emerge, was that C. imicola, the only proven vector of the virus of African horse sickness (AHS), was entirely absent. Though not abundant, C. bolitinos, a sister species of C. imicola, was overwhelmingly dominant (91 ,7%). Its larvae and pupae develop exclusively in the dung of cattle, but it is a species that is not implicated in the transmission of animal viruses. Elsewhere in South Africa, a frost-free climate, good rainfall and a plentiful supply of livestock would normally lead to the development of large foci of C. imicola. That this is not the case in the Port Elizabeth (P.E.) area is most likely owing to the winds inhibiting adult flight and the sandy soils being nutrient-poor and too well-drained to sustain Culicoides larvae. Studies are needed to confirm that sandy soils cannot sustain C. imicola. If so, the sandy coastal areas hold promise for quarantining against AHS.
Book review: Preventing the spread of aquatic animal diseases
(Published by the Agricultural Research Council, Onderstepoort Veterinary Institute, 1997) Anonymous; Verwoerd, Daniel Wynand
Guide for authors
(Published by the Agricultural Research Council, Onderstepoort Veterinary Institute, 1997) Anonymous; Verwoerd, Daniel Wynand
Predation of livestock ticks by chickens as a tick-control method in a resource-poor urban environment
(Published by the Agricultural Research Council, Onderstepoort Veterinary Institute, 1997) Dreyer, K.; Fourie, L.J.; Kok, D.J.; Verwoerd, Daniel Wynand
The possible use of chickens as predators of livestock ticks was studied. Chickens were allowed to scavenge for 3 h among tick-infested cattle in a typical township backyard during the milking period. Boophilus decoloratus, Hyalomma marginatum rufipes, Rhipicephalus evertsi evertsi and Otobius megnini were recovered from the crops and gizzards at necropsy. The numbers of ticks ingested ranged from 0-128, with an average of 28,81 (± 8,42) per chicken. This study has confirmed that chickens are natural predators of livestock ticks and that chickens can be used as part of an integrated tick control plan in urban cattle-management systems in resource-poor communities in South Africa.
The control of Glossina morsitans morsitans (Diptera: Glossinidae) in a settled area in Petauke District (Eastern Province, Zambia) using odour-baited targets
(Published by the Agricultural Research Council, Onderstepoort Veterinary Institute, 1997) Verwoerd, Daniel Wynand; Van den Bossche, Peter
A trial to control G. m. morsitans with the use of 980 odour-baited, insecticide-impregnated targets was conducted in a 300 km² area in the Eastern Province of Zambia between 1989 and 1991. The area is highly cultivated and cattle density is high (about 8 cattle/km²). Targets were deployed along roads and tracks. Deployment was restricted to suitable tsetse habitat. The effect of the targets on the tsetse population and on the transmission of tsetse-transmitted trypanosomosis was monitored by means of man-walked fly rounds and sentinel herds, respectively. The apparent density of tsetse in the trial area and in adjacent areas, declined rapidly after targets had been deployed. Trypanosomosis incidence in the trial area decreased significantly but did not completely disappear. Results from the trial show that odour-baited targets are effective in controlling Glossina m. morsitans in highly cultivated areas even when deployment is restricted to suitable tsetse habitat. It is concluded that tsetse control operations should be chosen such that either the invasion pressure is low from adjacent areas, or the size of the area is big enough, so that a central challenge-free area can be created.
Comparison of ELISA and HI for detection of antibodies against Wesselsbron disease virus
(Published by the Agricultural Research Council, Onderstepoort Veterinary Institute, 1997) Williams, R.; Schoeman, M.; Van Wyk, A.; Roos, K.; Josemans, E.J.; Verwoerd, Daniel Wynand
A two-graph Receiver Operating Characteristic analysis was done to determine the optimal cut-off value of an indirect enzyme-linked immunosorbent assay (ELISA) for detection of antibodies to Wesselsbron disease (WSL) virus. When ELISA and haemagglutination-inhibition (HI) results of WSL-positive and WSL-negative control sheep sera were compared, the sensitivity of ELISA was 97,9% and that of HI, 87,5%, while the specificity of ELISA and HI were 95,7% and 100 %, respectively. The ELISA's superior sensitivity was confirmed by the results of the two assays performed on a simulated range of low-positive sera, which showed that the ELISA was able to detect WSL-antibody levels at least ten times lower than those the HI could. The ELISA was also less cross-reactive than the HI to guinea-pig antisera against nine flaviviruses relevant to southern Africa. The combination of the ELISA's ability to test untreated sera in single dilution and its superior sensitivity and lower crossreactivity as compared to that of the traditional HI, makes it the assay of choice for automation and large-scale screening of animals for antibodies to WSL virus.
Seasonal abundance and parity of stock-associated Culicoides species (Diptera: Ceratopogonidae) in different climatic regions in southern Africa in relation to their viral vector potential
(Pretoria : Agricultural Research Council, Onderstepoort Veterinary Institute, 1997) Nevill, E.M.; Van der Linde, T.C. De K.; Verwoerd, Daniel Wynand; Venter, Gert Johannes
Seasonal abundance and parity in Culicoides populations, in the vicinity of livestock, were determined at seven sites in five different climatic regions with 220 V down-draught blacklight-traps. In 418 collections made between October 1983 and December 1986, a total of 2 134 171 Culicoides, of which 342 571 were identified to species level and sexed, were collected; 267 of these collections (182 321 Culicoides) were graded for parity. In the frost-free summer rainfall area, Culicoides were collected in large numbers in light-traps throughout the year; this implies breeding and possible virus transmission throughout the winter in certain parts of South Africa. However, where frost occurred, Culicoides numbers usually peaked in late summer and dropped sharply after the first frost. In the latter areas, small Culicoides collections during winter may be due to low winter temperatures and rainfall; low temperatures negatively affect adult activity and reduce the rate of development of larvae and pupae; low rainfall would lead to a reduction of available larval habitats. Relatively large numbers of Culicoides were collected in winter in the temperate frost-free winter rainfall area. In each of the four summer rainfall areas, one Culicoides species remained dominant throughout the year: at two of these areas this species was C. imicola. Other abundant species in some of these summer rainfall areas were C. schultzei s.I. and C. zuluensis. In the winter rainfall area, C. zuluensis, C. magnus, C. gulbenkiani and C. imicola shared abundance. It was established that abdominal pigmentation is an indicator of parity in C. imicola in South Africa. With the increase in Culicoides numbers towards the end of summer, there was also a rise in the proportion of parous (pigmented) females in most Culicoides species, which signifies a higher vector potential for African horsesickness and bluetongue towards the end of summer. This coincides with the seasonal occurrence of viral diseases transmitted by Culicoides species. Nulliparous (unpigmented) females of all Culicoides species were present throughout the year at all sites where Culicoides were continuously collected, confirming uninterrupted breeding in these areas.
Evaluation of a 3 ml heartwater (cowdriosis) infective blood vaccine dose
(Published by the Agricultural Research Council, Onderstepoort Veterinary Institute, 1997) Combrink, M.P.; De Waal, D.T.; Troskie, P.C.; Verwoerd, Daniel Wynand
Three milliliters of blood from the present commercially produced heartwater infective blood vaccine (Ball3 stock) was experimentally tested in sheep and cattle for infectivity and efficacy. Results obtained for this vaccine dose were statistically not different from results for the prescribed 5 ml vaccine dose.

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