An electron microscopic study of intra-erythrocytic stages of Babesia bovis in the brain capillaries of infected splenectomized calves.

Splenectomized vaccine donor calves undergoing primary reactions to Babesia bovis infections may develop cerebral babesiosis which leads to death if not treated in time. A brain biopsy was performed on an artificially-infected animal showing nervous symptoms and the tissue was immediately processed for electron microscopic examination. Virtually every erythrocyte in the brain capillaries sectioned was infected with B. bovis. Intra-erythrocytic merozoites, trophozoites and dividing trophozoites were indentified. Important features of the piriform merozoites included a reduced apical complex consisting of the anterior polar ring, microtubules, rhoptries and micronemes. Unidentified membrane-bound bodies, mostly spherical in shape, were observed anterior to the nucleus. The trophozoites showed very little structural differentiation and no food vacuoles or micropores could be detected. Each trophozoite produced 2 identical merozoites and the parent cell became totally incorporated in the daughter merozoites in the multiplication process. Projections were seen radiating from the surface of infected erythrocytes which appeared to adhere to other surfaces on contact. This probably resulted in the sludging of infected erythrocytes in the capillaries. The latter observations coincide with those described for Babesia argentina.

Negative staining of a non-haemadsorbing strain of African swine fever virus.

Since the application of negative staining, preceded by fixation, prevents the disruption and distortion of the capsid of the African swine fever virus, improved contrast and evaluation of the appearance and size of virus particles in the electron microscope is possible and, in addition, the icosahedral shape of the virus is demonstrable. The mature virus particle contains at least 2 capsid layers and an outer envelope.

The fine structure of intra-erythrocytic stages of Babesia bigemina.

The electron microscope was used to study the structure of merozoites, merozoites in the process of transformation to trophozoites, trophozoites, and the method of multiplication of B. bigemina. The merozoites were piriform in shape and surrounded by 3 peripheral membranes of which the 2 inner ones often appeared as a single thick osmiophilic structure (inner membrane). Anterior and posterior polar rings, microtubules, micronemes, rhoptries and mitochondria with and without tubular cristae were discernible. A single large unidentified spherical body was present in most of the mature merozoites. After penetration of an erythrocyte, merozoites developed into trophozoites through a transformation process which involved the loss of the inner membrane of the pellicle, rhoptries, most of the micronemes and the spherical body. The trophozoites were surrounded by a single membrane, were pleomorphic in shape and contained large inclusions of host cell cytoplasm, but no cytostomes or food vacuoles could be identified. Reproduction took place through a process resembling schizogony resulting in the production of 2 merozoites, the cytoplasmic constituents of the original trophozoite (mother cell) being virtually entirely incorporated into the daughter cells in the process. None of the parasites were contained in parasitophorous vacuoles.

Light and electron microscopic observations on the development of small merozoites of Babesia bovis in Boophilus microplus larvae.

The development of small pyriform merozoites of B. bovis in the granule-secreting cells of the salivary glands of B. microplus larvae, studied with a light microscope, showed a close resemblance to that of B. argentina described by Riek (1966) in the same tick vector. Dvelopment took place through a process of schizogony and resulted in the formation of many merozoites. A study of the ultrastructure of developing merozoites in the schizont revealed the following: a poorly defined outer membrane; a granular osmiophilic inner membrane; anterior and posterior polar rings; rhoptries; micronemes; microtubules; a nucleus; spherical bodies of varying size. The schizonts were membrane-bound but no parasitophorous vacuoles were seen.

Light and electron microscopic observations on the development of Babesia bigemina in larvae, nymphae and non-replete females of Boophilus decoloratus.

In Boophilus decoloratus infected by transovarian passage with B. bigemina, primary schizogony occurred as a continuous repetitive process in all 3 stages of the tick's life cycle spent on the host. The primary schizonts and the large merozoites (= vermicules) produced by them were observed in the gut epithelium, haemocytes, muscles, ad peritracheal cells. Secondary schizogony which led to the formation of small merozoites (= infective forms) occurred mainly in the salivary glands, but was also observed in the cortex of the synganglion. Mature small merozoites were observed in nymphal and adult ticks only. An infective stabilate was prepared from nymphae collected on Day 14 and Day 15 post larval infestation. The infections resulting from intravenous injection of the stabilate had a prepatent period of 8 days.

Transmission of jaagsiekte (ovine pulmonary adenomatosis) by means of a permanent epithelial cell line established from affected lungs.

An epithelial cell line, designated JS-15,4, has been established in culture from jaagiekte lesions and subcultured in vitro for almost 2 years. It exhibits morphological and other features of transformed cells and has been shown by electron microscopy to consist of type B ovine alveolar epithelial cells. Jaagiekte was successfully transmitted to 3 new-born lambs by the intratracheal injection of cells following immunosuppressive treatment with either anti-thymocyte immunoglobulin alone or combined with anti-macrophage immunoglobulin. Incubation periods as short as 10 weeks were recorded. Evidence was also obtained that natural transmission may result from the inhalation of viable cells.

The isolation and cultivation of calf rotavirus in the Republic of South Africa.

Calf rotavirus was cultivated and propagated in tissue culture from faeces of 3-week-old calves suffering from severe diarrhoea. Criteria for viral involvement were: production of cytopathic effect in primary foetal calf kidney cells, specific fluorescence, and identification of the agent by means of electron microscopy. In a limited serological survey the majority of the cows on an infested farm were found to possess neutralizing antibodies to the local rotavirus strain.

Studies on neonatal calf diarrhoea caused by rotavirus: transmission of the disease and attempted vaccination of colostrum-deprived calves.

Mild to severe scouring could be produced in colostrum-deprived calves with tissue culture-adapted rotavirus and feacal material from field cases of calf diarrhoea. The feaces of experimentally infected calves contained rotavirus for at least 3 days. Pathogenic bacteria were presented in one calf only and this calf also showed the most severe gastroenteritis. Eight calves were vaccinated with a live rotaviral calf diarrhoea vaccine and subsequently challenged with infective rotavirus. Mild scouring was observed after vaccination, but the calves remained normal after challenge. Rotavirus particles were detectable in the faeces for a few days after vaccination and challenge.

Scanning electron microscopy of Strongylus spp. in zebra.

The external ultrastructure of the anterior and posterior extremities of the nematodes, Strongylus asini , Strongylus vulgaris, Strongylus equinus and Strongylus edentatus, was studied with scanning electron microscopy (SEM). Fresh specimens of S. asini were collected from the caecum, ventral colon and vena portae of Equus burchelli and Equus zebra hartmannae ; S. vulgaris from the caecum, colon and arteria ileocolica of E. burchelli ; S. equinus from the ventral colon of E. z. hartmannae and S. edentatus from the caecum and ventral colon of both zebras , during surveys of parasites in zebras in the Etosha Game Reserve, South West Africa/Namibia, and the Kruger National Park, Republic of South Africa. The worms were cleaned, fixed and mounted by standard methods and photographed in a JEOL JSM - 35C scanning electron microscope (SEM) operating at 12kV . The SEM showed the following differences: the tips of the external leaf-crowns varied and were fine and delicate in S. asini , coarse and broad in S. vulgaris and, in S. equinus and S. edentatus, closely adherent, separating into single elements for half their length. The excretory pores showed only slight variation, and the morphology of the copulatory bursae did not differ from those seen with light microscopy. The genital cones differed markedly: S. asini had a ventral triangular projection and laterally 2 finger-like projections: in S. vulgaris there were numerous bosses on the lateral and ventral aspects of the cone; in S. equinus 2 finger-like processes projected laterocaudally ; and in S. edentatus 2 pairs of papilla-like processes projected laterally on the ventral aspects, and a pair of rounded projections and a pair of hair-like structures adorned the dorsal aspects.(ABSTRACT TRUNCATED AT 250 WORDS)

The fine structure of merozoites of Babesia bovis in the gut epithelium of Boophilus microplus.

Electron microscopic studies on merozoites of Babesia bovis in epithelial cells of the gut of Boophilus microplus revealed that the pellicle apparently consists of 3 membranes, and an osmiophilic layer intimately associated with microtubules. Micropores in the pellicle were often associated with micronemes. An unidentified tubular structure extended from the anterior polar ring to the nuclear region where it appeared to be associated with the nuclear envelope. A Golgi complex, typical protozoan mitochondria, food vacuoles and rhoptries could not be identified.

The isolation and attenuation of a virus causing rhinotracheitis in turkeys in South Africa.

In March 1978, a number of turkeys with severe respiratory symptoms affecting over 80% of the flock were investigated for a possible causative agent. With the standard techniques used for the isolation of bacteriae, mycoplasmae and viruses, only Mycoplasma gallisepticum, Mycoplasma meleagridis and Newcastle disease virus were isolated. Tracheal organ cultures were subsequently prepared from 27-day-old turkey embryos and inoculated with sinus exudate from affected turkeys. After an incubation period of 4 days a virus was isolated with which the typical symptoms, as observed in the field, could be reproduced in susceptible turkeys after 3-5 days. Following primary isolation in tracheal organ cultures, the virus grew readily in embryonated eggs and Vero cells. With the electron microscope, virus-like particles, varying in size from 40 nm-500 nm, were observed, having a pleomorphic shape and studded with fine surface projections. The virus seems to fall into the family Paramyxoviridae. A vaccine produced from attenuated virus in embryonated eggs afforded good protection against mortalities due to airsacculitis that normally follows on to turkey rhinotracheitis infection. The serological and clinical effects of the virus on chickens are also reported on.

A comparison of fixatives suitable for scanning electron microscopy of Habronema spp.

Members of the genus Habronema (Nematoda: Habronematidae) were preserved in 4 fixatives for examination with scanning electron microscopy (SEM). Tegumental features of the anterior and posterior extremities of these specimens were compared to evaluate the effect of the fixatives: modified Flemming's solution, glutaraldehyde (GA), Karnovsky's fixative and 70% ethanol. Fixatives were assessed on the appearance of the tegument, evidence of any wrinkling, shrinkage or swelling and the degree of extension in the male tail. Seventy per cent ethanol gave the most satisfactory results.

Viruses isolated from Culicoides midges in South Africa during unsuccessful attempts to isolate bovine ephemeral fever virus.

Five viruses, unrelated to bovine ephemeral fever virus (BEFV), were isolated from Culicoides biting-midges collected during the summer months of the years 1968-69 and 1969-70 near a cattle herd in which cases of BEF occurred and at an open horse stable at Onderstepoort. These viruses were investigated by means of serological, electron-microscopical and physicochemical tests. It was established that 2 isolates, Cul. 1/69 and Cul. 2/69, were related to each other and belonged to the Palyam subgroup of the genus Orbivirus, that isolate Cul. 3/69 belonged to the equine encephalosis subgroup of the genus Orbivirus, while Cul. 1/70 was related to Akabane virus, which belongs to the Simbu subgroup of the family Bunyaviridae. One isolate, Cul. 5/69, though prevalent in the cattle population, could not be identified at this point. A brief serological survey indicated that the cattle in the nearby herd possessed antibodies against all the isolates except Cul. 3/69. BEFV could not be isolated in mice or in cultured cells from the wild-caught Culicoides.

Viruses and virus-like particles identified in ostrich gut contents.

Samples of either gut content from ostriches showing symptoms of enteritis, or allantoic fluid of eggs inoculated with ostrich isolates, were examined for the presence of viral agents by direct negative-contrast electron microscopy. Only a few virus types could be identified with certainty, namely a circovirus (1 sample), a coronavirus (1 sample), a member of either the toga- or bunyaviridae (1 sample), enterovirus (16 samples) and paramyxovirus (26 samples). A large number of samples contained structures resembling myxovirus particles that were interpreted as fringed membranous particles of non-viral origin. An unusual observation of probable single-strand nucleocapsid helices, possibly originating from digested plant material and which were identified in a number of small intestine samples, is reported. This is the 1st report of a spectrum of viruses and virus-like particles occurring in enteric samples from ostriches in South Africa. The low incidence and variety of viruses reported here contribute to the multifactorial origin and complexity of enteric disease in ostriches as well as in other birds and mammalian species.

Scanning electron microscopy of Bunostomum phlebotomum (Railliet, 1900).

Live specimens of Bunostomum phlebotomum were collected from the small intestine of a calf and processed for scanning electron microscopy using standard methods. This paper describes the surface morphology of adult worms. All these hookworms showed a dorsally bent anterior end with its buccal capsule, which opens antero-dorsally with a pair of chitinous cutting plates on the ventral margin. Prominent cervical papillae and a well developed male bursa with a dorsal and 2 lateral lobes, were observed. The female tail is slender and pointed with the anal opening close to the tip. Further studies are necessary to demonstrate morphological differences from other hookworms and to obtain more detail of the male bursa and female tail.

Swollen head syndrome in chickens: a preliminary report on the isolation of a possible aetiological agent.

An extremely pleomorphic virus was isolated from broilers with swollen head syndrome. This virus seems to be related to the virus causing turkey rhinotracheitis.

Besnoitiosis in a horse.

Besnoitiosis was confirmed in a pony which presented with inspiratory dyspnoea, scleroderma and ventral oedema. Numerous cysts were visible in the sclerae. Histological examination of the skin confirmed the presence of numerous cysts. The parasite could not be transmitted by subcutaneous injection of homogenised skin from the infected horse to rabbits and a horse. Ultrastructural morphology of the crescent-shaped bradyzoites was not compatable with Besnoitia besnoiti or B. jellisoni and it is proposed that the infection was caused by B. bennetti.

Rotavirus in Saanen goats.

Rotavirus particles were detected in the stools of 8 out of 12 Saanen kids with either diarrhoea or an increased rectal temperature. No other pathogenic organisms could be recovered from these kids. This is believed to be the first report of rotavirus infection in goats in southern Africa.