Toxocara vitulorum: maternal transfer of antibodies from buffalo cows (Bubalis bubalis) to calves and levels of infection with T vitulorum in the calves.

The levels of antibody to the excretory/secretory antigens of the infective larvae and adults of Toxocara vitulorum were measured by gel precipitation and ELISAs in the serum and colostrum of 12 buffalo cows naturally infected with T vitulorum and in the serum of their calves. The antibody levels were compared with the extent of T vitulorum infection as judged by faecal egg counts in the calves. The patterns of bands of the larval antigens and gel precipitating antibodies in cow serum taken one month before calving, in cow colostrum and in calf serum were very similar. Nine cows and their calves had gel precipitating antibodies but the remaining three cows and their calves did not. The ELISA detected anti-larval antibodies in the colostrum of all 12 cows and calves. With the exception of one calf there was a strong correlation (r = 0.902) between the antibody titre in cow colostrum and the titre of passively acquired antibody in calf serum. The titres of these passively acquired antibodies declined to their lowest levels in calves 12 to 25 days of age; the antibody concentrations then began to increase up to day 42 and remained stable for the remainder of the experiment (105 days). The titres of antibodies to the antigens of the adult worms, examined in four cows and their calves, were lower than the titres to the larval antigens; the calves absorbed this anti-adult antibody from the colostrum and the antibody levels reached a plateau between days 12 and 30 and remained stable for the rest of the experiment.(ABSTRACT TRUNCATED AT 250 WORDS)

Periparturient reduction in buffalo of mitogen-induced lymphocyte proliferation and antibody to Toxocara vitulorum.

Lymphocyte and antibody reactivity were examined during the periparturient period in buffalo cows naturally infected with Toxocara vitulorum. Titres of antibodies to an extract of T. vitulorum larvae increased about 3 months before parturition. Antibody titres declined at about the time of parturition and remained low for up to 3 months into lactation. Lowered titres were found in the IgG class and not the IgM class of immunoglobulins. Levels of lymphocyte transformation induced by the mitogens concanavalin A and pokeweed mitogen declined markedly from one to 2 weeks before until one to 2 weeks after parturition. The relationship between this suppressed immunological reactivity and vertical transmission of T. vitulorum larvae is discussed.

The effect of serum and colostrum immunoglobulins from buffaloes infected with Toxocara vitulorum on T. vitulorum larvae in vitro and in vivo in mice.

Serum and colostrum were collected from adult buffalo cows naturally infected with Toxocara vitulorum. When injected into mice, the colostrum reduced the number of larvae of T. vitulorum that migrated in the mice. Injection of particularly the IgG-containing fraction but also the IgM-containing fraction of Sephadex G200-chromatographed colostrum also passively protected mice. When incubated for 6 h in buffalo serum or colostrum or fractions of these from Sephadex G200 and diethylaminoethanol Sephadex, T. vitulorum larvae had their activity in vitro curtailed. When the larvae were then fed to mice, their ability to migrate was markedly inhibited as compared with that of larvae that had been incubated in fetal calf serum or in helminth-free sheep colostrum. Fractions of serum and colostrum containing IgG1 had greater inhibitory effects both on the larvae in vitro and on their subsequent migration in mice than did IgG2-containing fractions. IgM also inhibited the larvae as 2-mercaptoethanol reduction of IgM in the IgM-containing peak eluted from Sephadex G200 reduced the inhibitory activity of this peak, although the activity was not completely abrogated.

Collection of eggs and hatching and culturing second-stage larvae of Toxocara vitulorum in vitro.

Eggs of Toxocara vitulorum were harvested from the feces of infected buffalo calves and embryonated in vitro. Optimum conditions for hatch and culture of the second-stage larvae were determined. Maximum hatch of larvae occurred from eggs that were decoated by treatment with saturated Ca(OCl)2 for 16-24 min followed by treatment with CO2 and incubation at 37 C. Larvae could be cultured in RPMI-1640 medium for up to 3 mo but survived for only 3 wk in Eagle's minimum essential medium.

Antigen-induced protection against infection with Toxocara vitulorum larvae in mice.

Larvae of Toxocara vitulorum hatched and migrated in the tissues of normal mice. Larvae survived in reasonable numbers, particularly in the liver and, to a lesser extent, in the lungs and kidneys, for at least 4-7 days and in muscles, albeit only in low numbers, for at least 3 weeks. Oral infection of mice on three or more occasions with T. vitulorum eggs induced protection against a challenge infection with eggs of T. vitulorum. Prior parenteral immunization of mice with a variety of T. vitulorum soluble antigens (extracts, excretions/secretions, or perienteric fluid and their fractions) from adult parasites and/or infective larvae induced statistically significant protection against infection. The most effective protective immunogens were three or more injections with perienteric fluid from adults (100% protection) and excretions/secretions from infective larvae of T. vitulorum (> 92% protection).

Toxocara vitulorum in the milk of buffalo (Bubalus bubalis) cows.

The duration of excretion of Toxocara vitulorum larvae in the milk of buffalo cows determines the optimum time for treating calves. Studies on 10 cows showed that a few larvae occur in the colostrum of some cows before the calf has suckled, but most are present from the day after calving and for a further five days. From day 9 onwards, very few larvae were found in the milk. The total number of larvae found was comparable with the number of adult parasites collected from the calves of cows with similar histories. The larvae were 1254 +/- 60 microns long and 36 +/- 6.7 microns in diameter at the ventriculus, figures which are substantially different from some published results.

The significance of the gastrointestinal parasites of Asian buffalo in Sri Lanka.

Buffalo aged 3-15 months on institutional farms and in the villages of an irrigation project were monitored for gastrointestinal nematodes by faecal egg counts over two years. Apart from treatment for Toxocara vitulorum at 10-16 days of age, no anthelmintics were used. Half of the strongylid egg counts were zero and 90% were less than 500 epg of faeces on the institutional farms, and 67% were zero and 97% less than 500 epg in the villages. No problems arose during four years without anthelmintics on the institutional farms and during two years in the villages. Autopsies demonstrated that the eggs which were present were produced by mixed infections of small numbers of Haemonchus spp., Mecistocirrus digitatus, Trichostrongylus spp., Bunostomum phlebotomum and Cooperia spp. High egg counts of Strongyloides papillosus occurred in calves up to six months old, but were not pathogenic.

Relative importance of larval and adult Mecistocirrus digitatus in inducing resistance to a reinfection in calves.

Calves immunized with adult Mecistocirrus digitatus implanted directly into the abomasum did not develop a substantial degree of immunity to a subsequent large oral (challenge) dose of larvae, which developed to maturity. In contrast animals immunized by oral infection developed strong resistance. The calves implanted with adult worms appeared to show a greater degree of susceptibility to maturation of the challenge infection than controls which received a challenge of the same magnitude without any previous immunization. The implanted female adult worms established in the hosts and continued to produce more eggs for a longer time than those which developed to maturity from the oral immunizing infection with third-stage larvae. Passive haemagglutination studies revealed that the implanted adult worms stimulated little or no antibody response in the hosts. In the calves which did not show a response to the adult worm implant the subsequent challenge with an oral infective dose of third-stage larvae also failed to stimulate a response. Likewise the two calves from the group which showed a weak antibody response to the adult worm implant did not show an increased response when challenged. In contrast, calves immunized with an oral infection of third-stage larvae had an antibody response which showed a vigorous rise on challenge in four of the five calves. Thus a direct relationship between resistance to challenge infection and the antibody response determined by the passive haemagglutination and gel-diffusion tests was observed in the calves immunized orally.