Long-Term Study of Toxoplasma gondii Infection in a Swedish Sheep Flock

Lundén, A., A. Näsholm and A. Uggla: Long term study of Toxoplasma gondii infection in a Swedish sheep flock. Acta vet. scand. 1994,35,273-281.– The infection rate of Toxoplasma gondii was studied during 6 years in a sheep flock in central Sweden. The flock consisted of 165-249 breeding ewes of which 20-35% were lambs less than 1 year old. Most ewes were slaughtered when 5 years old. The sheep were kept indoors from end of September to early May. Lambing took place in March and April. Individual serum samples were collected twice a year, once just before turning the sheep out to pasture in the spring, and again after housing in the autumn. Sera were analysed by ELISA for antibodies to T. gondii. The seroprevalence varied between 10% and 45% during the 6 years of observation. Seroconversion was detected predominantly at the autumn sampling, indicating that in most cases infection was acquired at pasture. Subclinical effects of T. gondii infection on lamb weight, litter size, total litter weight and ewe weight were also studied. Lambs born to chronically infected ewes were lighter at birth than those of uninfected ewes, but this disparity was no longer evident at weaning.     

Ovine toxoplasmosis in Sweden

Sera from 155 ewes representing 21 different sheep flocks from the central parts of Sweden were examined for the presence of antibodies to Toxoplasma gondii by the indirect fluorescent-antibody test. Seropositive animals were found in 14 flocks, which corresponded to 55 % of the tested sera. Animals from the same flock were with few exceptions either all positive or all negative. Some ewes with a history of abortion a few months before blood sampling showed high titers indicating causative correlation with toxoplasmosis. These are the first verified cases of ovine toxoplasmal abortions in Sweden.Key words: Toxoplasma gondii, sheep, abortion, fluorescent antibody test     

A Serological Study on The Prevalence of Toxoplasma Gondii in Meat-Producing Animals in Sweden

Sera from 200 sheep, swine and cattle, respectively, collected at slaughter at each of 3 abattoirs situated in the north, middle and south of Sweden were examined for the presence of antibodies to Toxoplasma gondii by the indirect fluorescent antibody test. Seropositive animals (titre ≥ 1:20) were found at the following rates from north to south: sheep 60%, 66% and 68.5%, swine 9%, 2.5% and 37%, and cattle 10%, 6 % and 35%. The significance of the serological findings is discussed, and it is concluded that T. gondii infection is common in Swedish farm animals. Thus the meat from particularly swine and sheep may provide a potential source of human toxoplasmosis.     

Isolation of Neospora caninum from a calf in Malaysia

In order to attempt isolate the protozoan parasite Neospora caninum, an N. caninum seropositive pregnant Sahiwal Friesian cross heifer from a large-scale dairy farm in Malaysia was kept for observation until parturition at the Veterinary Research Institute, Ipoh. The heifer gave birth to a female calf that was weak, underweight and unable to rise. Precolostral serum from the calf had an N. caninum indirect fluorescent antibody test titre of 1:3200. It died 12 h after birth and necropsy was performed. Brain homogenate from the calf was inoculated into 10 BALB/c mice that were kept for 3 months after which brain tissue from the mice was inoculated onto 24 h fresh monolayer Vero cell lines. The cell cultures were examined daily until growth of intracellular protozoa was observed. DNA of the organisms from the cell cultures was analyzed by PCR and DNA sequencing. DNA fragments of the expected size were amplified from the isolate using N. caninum-specific primers, and sequence analysis of ITS1 clearly identified the isolate as N. caninum. This is the first successful isolation of N. caninum from a bovine in Malaysia, and the isolate is designated Nc-MalB1.     

Characterization of coagulase negative staphylococci from cases of subclinical mastitis in dairy cattle in Kampala,Uganda

Background

Coagulase negative staphylococci (CNS) are the most common pathogens leading to subclinical mastitis (SCM) in dairy cattle in Uganda. Coagulase negative staphylococci can vary between bacterial species in how they cause disease. The aim of the study was to characterize CNS, from cows with SCM in Uganda, at the species level.

Findings

Quarter milk samples (n = 166) were collected from 78 animals with SCM. Bacteriological analyses were carried out at Makerere University, Kampala, Uganda and at the National Veterinary Institute (SVA), Uppsala, Sweden. The most common pathogens found in milk samples from cows with SCM were CNS (31.7%). Two species of CNS were found, S. epidermidis (85%) and S. haemolyticus (15%). Of the CNS isolates, 16/20 (80%) were positive for β-lactamase production (β+).

Conclusions

In milk samples from cows with SCM caused by CNS, S. epidermidis was most prevalent, followed by S. haemolyticus.     

Application of the Neospora caninum IgG avidity ELISA in assessment of chronic reproductive losses after an outbreak of neosporosis in a herd of beef cattle.

Point-source infections are most likely the cause for Neospora caninum-induced abortion outbreaks in cattle, whereas an increased annual abortion rate may be a consequence of vertical transmission. The aims of the present study were to examine the reproductive effects of neosporosis in a beef herd for 3 years, after a point-source outbreak and to use IgG avidity serology to examine the chronicity of infections and patterns of transmission. During the study, 76-78% of animals were seropositive for N. caninum. The pregnancy rate varied from 88% to 94%, without any reduction in the pregnancy rate of seropositive cows compared with seronegative cows. The annual abortion rate was 2.5-5.5%, and all but 1 abortion occurred in seropositive dams. The efficiency of vertical transmission was estimated to be 85%. Several calves, born to seronegative dams, were seropositive at 6-13 months of age, indicating a 22% mean annual rate of horizontal transmission. The mean avidity in seropositive cows increased from 30 during the initial outbreak to 74 after 3 years. The mode of IgG avidity was 21-40 during the initial abortion outbreak, 41-60 after 1 year, and 61-80 after 2 and 3 years. The results reveal high annual rates of both vertical and horizontal transmission of N. caninum in a herd of beef cows and provide further validation on the ability of the N. caninum IgG avidity ELISA to accurately assess the chronicity of infection.     

Purification and identification of water-soluble phosphopeptides from cheese using Fe(III) affinity chromatography and mass spectrometry

Water-soluble phosphopeptides from cheese were isolated using immobilized metal affinity chromatography (IMAC). Phosphopeptides from aqueous cheese extracts were completely retained on iminodiacetic acid (IDA) Sepharose equilibrated with FeCl3 and subsequently eluted with ammonium dihydrogen phosphate. Peptides in the eluate from the IMAC-Fe(III) column were identified using reversed phase liquid chromatography-electronic spray identification-tandem mass spectrometry. Phosphopeptides from two different cheeses were analyzed using the described method: a 10-month-old semihard Herrgard cheese made with mesophilic starter and a 24-month-old Parmigiano Reggiano cheese made with thermophilic starter. Elution of the IMAC-Fe(III) column with a gradient of ammonium dihydrogen phosphate resulted in three distinct peaks for Herrgard cheese corresponding to peptides carrying one, two, and four phosphorylated serine residues, respectively. Sixty-five different phosphopeptides were identified from the Herrgard, whereas only 9 from the Parmigiano Reggiano.