A granular vulvitis syndrome associated with ureaplasma infection was first recognized in Ontario dairy herds in 1972.
The acute form of the disease was characterized by a purulent vulvar discharge, an inflamed hyperemic vulvar mucosa and varying degrees of granularity. In the chronic form, there was an absence of a purulent discharge and a gradual decline in the severity of the hyperemia and granularity. Epithelial inclusion cysts were observed in the vulvar epithelium of approximately 10% of affected cows.
A seasonal variation in the incidence of the disease was observed. Herd morbidities during the summer months reached a low of 37% and increased to 75% during the winter months with constant housing.
When widespread in herds, the acute form of the disease had a significant effect on fertility. In four herds examined, first service conceptions dropped on average by 27%.
The chronic form of the disease had a less detrimental effect on fertility with first service conceptions being reduced on average by 13%.
Intrauterine infusions of a tetracycline 24 hours postbreeding were found to be of value in improving conception rates in acutely affected herds.
Granular vulvitis was reproduced in ten virgin heifers following vulvar inoculation with strains of ureaplasma previously isolated from natural cases. The disease appeared one to three days postinoculation and was characterized by vulvar swabs but not from the upper mucopurulent discharge. At necropsy 13 to 41 days later, ureaplasmas were recovered consistently from vulvar swabs but not from the upper reproductive tract. It was concluded that some strains of ureaplasma are pathogenic and should be viewed as a cause of bovine granular vulvitis.
We report herein a survey in which cultures of bovine reproductive tracts for Ureaplasma diversum and mycoplasmas were carried out in order to better understand the role of these organisms in granular vulvitis (GV). Samples cultured were vulvar swabs from clinically normal cows or ones with GV, preputial swabs or raw semen from bulls, and abomasal contents of aborted fetuses.
Ureaplasma diversum was isolated from 104 (43.3%) of 240 dairy cows, 32 (27.1%) of 118 beef cows, 43 (47.2%) of 91 beef heifers, 23 (67.6%) of 34 beef bulls, and three (60%) of five dairy bulls. Mycoplasmas were isolated from 18 (7.5%) dairy cows, two (1.6%) beef cows, three (8.8%) beef bulls, and one dairy bull. No isolation was made from 97 aborted fetuses. For 65 dairy cows and 30 beef heifers with vulvar lesions, the isolation rates for ureaplasmas of 62.5% and 69.7%, respectively, were significantly higher (X2) than those for normal animals (37.5% and 30.3%). On immunofluorescent serotyping of 137 of the 205 isolates, there were 66 in serogroup C (strain T44), 18 in serogroup B (strain D48), eight in serogroup A (strain A417 or strain 2312), 14 cross-reacting, and 31 that were not identified. It was concluded that U. diversum is commonly present in the lower reproductive tract of beef/dairy cattle in Saskatchewan and is associated with granular vulvitis.
Twenty-three virgin Holstein heifers received uterine inoculations with ureaplasma and were necropsied one to thirteen days later. Three heifers inoculated intracervically were necropsied on days 3, 5 and 11.
Granular vulvitis was produced on average by 3.6 days in fourteen of sixteen uterine inoculated heifers monitored for four or more days. Two cervically inoculated heifers monitored for over four days also developed granular vulvitis by the fourth day.
At necropsy, ureaplasma was recovered from 94% of uterine horn cultures for the first four days postinoculation and 50% during days 5 to 7. Thereafter all uterine cultures were negative. The percentage of positive ureaplasma recoveries from uterine tube flushings was lower than for uterine horns but remained positive for a longer period. By day 7, three of four uterine tube flushings were still positive. No bacterial pathogens were isolated from the uterine horns or uterine tube flushings.
On histopathology 50% of uterine inoculated heifers had endometritis up to six days postinoculation and a slightly higher percentage (58%) had salpingitis. Endometritis was not found in any heifers after day 6. Residual salpingitis was present in one heifer on day 7. Endometritis was present in cervically inoculated heifers necropsied on days 3 and 5 but not on day 11. Salpingitis was not found in any of the three cervically inoculated animals.
The study concluded that some strains of ureaplasma are pathogenic for the upper reproductive tract of the cow and should be considered significant when isolated from cases of granular vulvitis, endometritis or salpingitis.
Vulvitis chronica plasmacellularis or Zoon's vulvitis is a rare benign circumscribed inflammation of the vulvar mucosa. It is found in women ranging in age from 26 to 70 years. Shiny, macular erythematous lesions, which are irregular in shape and sharply marginated are usually observed. The histologic findings show chronic subepithelial dense inflammation composed largely of plasma cells. We here report two cases of vulvitis plasmacellularis with typical clinical manifestations, courses and histopathologic findings.
Samples of cervico-vaginal mucus from 633 animals from 110 herds were cultured and yielded the following mycoplasmas: T-strain--88: Mycoplasma bovigenitalium--79, Mycoplasma spp. (Leach Group 7)--7, Acholeplasma laidlawii--4, Mycoplasma bovirhinis--2 and one not typable. Uterine exudates and endometrial scrapings from 80 infertile cows in two herds were examined. Four animals were positive, M. bovigenitalium was isolated three times, A. laidlawii and Mycoplasma arginini once each. Sixty-five normal uterine contents from pregnant cows were examined, one yielded M. bovigenigalium and the same organism was recovered from the fetal kidney. T-strain mycoplasma, M. bovigenitalium and other Mycoplasma spp. appear to be a part of the normal flora of the cervico-vaginal region of clinically normal one and two year old bred heifers in Alberta and Saskatchewan. Although M. arginini was not recovered from the cervico-vaginal region, a single recovery was made from the uterus of an infertile cow.
The genital mycoplasma and ureaplasma flora was compared in 136 dogs with varied reproductive histories. Mycoplasmas were recovered from 88% of vulvovaginal swabs, 85% preputial swabs and 72% semen samples. Isolation rates were slightly higher from dogs that were infertile or had evidence of genital disease but the differences from those that were fertile or clinically normal were statistically significant only in the male. Ureaplasmas were recovered from half the females sampled. Higher, but not statistically significant isolation rates (75%) were made from infertile females with purulent vulvar discharge versus those that were clinically normal and fertile (40%). In the male dog there was a significantly higher incidence of ureaplasmas in the prepuce of infertile animals (69%) than those that were fertile (0%) (p less than or equal to 0.05). Semen isolations although not significantly higher in infertile males, were all made from ejaculates, with subnormal motility, low sperm counts and/or a high percentage of midpiece and tail abnormalities (bent or tightly coiled).
In a case of acute Reiter's syndrome with severe vulvitis the diagnosis was based on the presence of a vaginal discharge and dysuria, arthritis, conjunctivitis, buccal ulceration, keratodermia blenorrhagica, and HLA B27 tissue-typing antigen. The vulval lesions were similar in appearance to those of circinate vulvitis. The acute histological change were confined to shallow ulceration with an inflammatory infiltration of the subjacent dermis. Coincidential lichen sclerosus et atrophicus was present, which could have been masked by the acute lesions.
Infection, lesions and clinical significance of Acheloplasmas, Mycoplasma bovis and Mycoplasma bovigenitalium in genital disease of cattle are described. A more detailed account is given of ureaplasma infections. Acute and chronic forms of granular vulvitis in both field and experimental disease are described as well as the role of the organism in abortion.
Recovery rates of ureaplasma and mycoplasma from semen and preputial washings in bulls are outlined and their significance in disease is discussed. There are problems in differentiating pathogenic from nonpathogenic isolates. Methods are being developed to treat semen for these organisms.
This paper provides a concise summary of clinical and microbiological aspects of bovine genital mycoplasmosis.
Bovine mastitis caused by Mycoplasma agalactiae subsp. bovis was first diagnosed in 16 of 55 cows in an Ontario herd in Feburary 1972. A total of 182 of 598 (30.4%) cows from 33 of 64 (51.5%) farms in widely separated areas of the province were culturally positive. Herd incidence varied from 15 to 40% with one closed herd having an incidence of 61%. Four herds were investigated culturally and serologically by the growth inhibition test for 15 months. In the acute phase the organism was present in the milk in extremely high numbers and could still be isolated from a few cows after eight to 12 months. The sera from 89.5% of the animals with clinical mycoplasma mastitis produced a zone of surface "film" and/or colony inhibition and some cows remained positive for six to 12 months. The disease was experimentally reproduced with a pure culture of the organism isolated from the milk of a cow from one of the herds.
A streptococcus epidemic of moderate extent and severity was characterized by clinical symptoms different from the usual septic sore throat, though the organism found was culturally Streptococcus epidemicus. The infection was traced to the milk from a single quarter of the udder of a cow in a dairy of 112 cows producing an otherwise excellent grade of raw milk. A number of the milkers on the dairy farm were found infected. It was impossible to trace the infection of the cow's udder to any one of the milkers, though such an infection seems probable since the streptococcus isolated from the cow was in every respect like streptococci isolated from patients and milkers, and different from those usually found in normal cows or cows with garget. Certain recommendations are made to safeguard producers of raw milk against the occurrence of such epidemics.
Two cases of Reiter's syndrome in women are described. The diagnosis was based on the presence of increased vaginal and cervical discharge containing excess leucocytes, arthritis, conjunctivitis, and HLA B27 tissue-typing antigen. In addition circinate lesions developed on the vulva similar to those seen on the glans penis. No previous description of these lesions has been traced and the name 'circinate vulvitis' is suggested for these lesions.
The clinical attributes of 40 dairy cows which had mastitis but no growth of bacteria from the milk were analyzed and compared to the attributes in 102 cows with only gram-positive and 61 cows with only gram-negative bacteria cultured from the milk. Cows with no bacteria cultured from the milk did not differ significantly from cows with gram-positive bacteria cultured, but 9 of 12 attributes were significantly different between cows with no bacteria cultured and cows with gram-negative bacteria cultured. Discriminant analysis was used to classify cows as members of the gram-positive or gram-negative culture groups. The discriminant equation was then applied to the cows with no bacteria cultured, and 78% of cows with no bacteria cultured were classified as members of the gram-positive group. Most mastitis in cows with no bacteria grown from the milk was probably due to gram-positive bacteria. If antibiotic therapy is used in cows with persistent mastitis and a negative culture in the belief that the culture is a false negative, treatment with antibiotics effective only against gram-negative organisms would not be appropriate.
This is the first study describing an experimental mastitis model using transgenic cows expressing recombinant human lactoferrin (rhLf) in their milk. The aim of the study was to investigate the concentrations in milk and protective effects of bovine and recombinant human lactoferrin in experimental Escherichia coli mastitis. Experimental intramammary infection was induced in one udder quarter of seven first-lactating rhLf-transgenic cows and six normal cows, using an E. coli strain isolated from cows with clinical mastitis and known to be susceptible to Lf in vitro. Clinical signs were recorded during the experimental period, concentrations of human and bovine Lf and indicators of inflammation and bacterial counts were determined for milk, and concentrations of acute-phase proteins and tumor necrosis factor alpha were determined for sera and milk. Serum cortisol and blood hematological and biochemical parameters were also determined. Expression levels of rhLf in the milk of transgenic cows remained constant throughout the experiment (mean, 2.9 mg/ml). The high Lf concentrations in the milk of transgenic cows did not protect them from intramammary infection. All cows became infected and developed clinical mastitis. The rhLf-transgenic cows showed milder systemic signs and lower serum cortisol and haptoglobin concentrations than did controls. This may be explained by lipopolysaccharide-neutralizing and immunomodulatory effects of the high Lf concentrations in their milk. However, Lf does not seem to be a very efficient protein for genetic engineering to enhance the mastitis resistance of dairy cows.
Ureaplasma diversum has been associated with infertility in the cow experimentally and in naturally occurring cases. However, the pathogenic mechanism is undetermined. The purpose of this study was to determine whether ureaplasmas are pathogenic for bovine morulae in vitro. Twenty-one morulae were recovered from three superovulated, mature, Holstein cows six or seven days postestrus. The embryos were divided into three groups (A,B,C) and incubated for 16 hours at 37 degrees C in humidified air with 10% CO2. Group A was incubated in embryo culture medium alone, Group B was incubated in culture medium with sterile ureaplasma broth added and Group C was incubated in culture medium containing 1.7 X 10(6) colony forming units Ureaplasma diversum strain 2312. After incubation, the morulae were examined using an electron microscope. Structures morphologically identical to U. diversum were present on the outer surface of the zonae pellucidae of all the morulae exposed to the organism and none were present on the unexposed control embryos. No other morphological differences were observed in either the ureaplasma-exposed embryos or the two groups of control embryos. Ureaplasma diversum was isolated from three of the five embryos incubated in culture medium with sterile ureaplasma broth added. These three embryos were recovered from one donor cow which cultured positive for U. diversum from the vulva and flush fluid. This finding suggests that the contaminating organisms entered the embryo culture wells either in the embryo collection medium or attached to the embryos.(ABSTRACT TRUNCATED AT 250 WORDS)
"Haemophilus somnus" has been identified in the etiology of bovine abortion on the basis of the isolation of the organism from aborted fetal and placental tissues. To investigate the role of hematogenous dissemination of "H. somnus" in the pathogenesis of abortion and to monitor the humoral immune response to infection, 19 pregnant cows (gestation ages, 1.4 to 7 months) were challenged intravenously (11 cows) or intrabronchially (8 cows). Five cows challenged intravenously aborted, and one cow challenged intrabronchially resorbed her fetus. "H. somnus" was isolated in large numbers from aborted tissues, and placental lesions were similar to those reported in a field case of "H. somnus" abortion. Antibody titers in serum were measured by the microagglutination test (MAT) and by enzyme-linked immunosorbent assay (ELISA). A response to challenge was measured by MAT; it was also measured by ELISA within the immunoglobulin G1 (IgG1), IgG2, and IgM isotypes. On comparison of pre- and postchallenge antibody titers, the greatest and most persistent response was detected within the IgG2 isotype. Prechallenge antibody titers (measured by MAT and by IgG2 ELISA) were lower in animals that aborted than in normal calving animals, indicating that IgG2 antibody may have a role in limiting hematogenous dissemination of "H. somnus."
The focus of this study was Salmonella enterica serotype Cerro, a potentially emerging pathogen of cattle. Our objectives were to document the within-herd prevalence of Salmonella Cerro among a sample of New York dairy herds, to describe the antimicrobial resistance patterns and pulsed-field gel electrophoresis types of the isolates, and to elucidate the status of this serotype as a bovine pathogen. Data were collected prospectively from dairy herds throughout New York that had at least 150 lactating cows and that received clinical service from participating veterinarians. Following enrollment, Salmonella surveillance consisted of both environmental screening and disease monitoring within the herd. Herds positive by either environmental or fecal culture were sampled during three visits to estimate the within-herd prevalence of Salmonella. Among 57 enrolled herds, 44 (77%) yielded Salmonella-positive samples during the study period. Of these, 20 herds (46%) were positive for Salmonella Cerro. Upon follow-up sampling for estimation of prevalence, Cerro was identified in 10 of the 20 herds; the median within-herd Cerro prevalence was 17%, with a maximum of 53%. Antimicrobial resistance ranged from zero to nine drugs, and eight (40%) of the Cerro-positive farms generated drug-resistant isolates. Eight XbaI pulsed-field gel electrophoresis types were represented among 116 isolates tested, although 89% of these isolates shared the predominant type. Among herds with clinical cases, cattle that had signs consistent with salmonellosis were more likely to test positive for Cerro than apparently healthy cattle, as estimated by a logistic regression model that controlled for herd as a random effect (odds ratio: 3.9). There is little in the literature concerning Salmonella Cerro, and published reports suggest an absence of disease association in cattle. However, in our region there has been an apparent increase in the prevalence of this serotype among cattle with salmonellosis. Other Salmonella serotypes important to bovine health have emerged to become leading causes of human foodborne disease, and close monitoring of Cerro is warranted.
The aim of this study was to detect the associations between bovine herpesvirus 1 (BHV-1) status of a herd and respiratory disease (BRD) occurrence and reproductive performance in pregnant heifers and cows. The association between management-related factors and higher BRD occurrence was also estimated.
Serum samples, collected from cows and youngstock from 103 dairy cattle herds, were analyzed for antibodies against BHV-1, bovine respiratory syncytial virus (BRSV), bovine viral diarrhoea virus (BVDV), and Mycoplasma bovis. A questionnaire was used to collect data concerning herd management factors and reproductive performance, as well as the occurrence of clinical signs of respiratory disease in the last two years, as evaluated by the veterinarian or farm manager. Multiple correspondence analysis (MCA) and logistic regression analysis were performed to identify and quantify the risk factors.
A low to moderate prevalence (1-49%) of BRSV antibodies among youngstock was associated with a high occurrence of respiratory disease (OR = 6.2, p = 0.010) in cows and in-calf heifers. Employees of the farm may participate in the spread of such disease. Larger herd size, loose-housing of cows, housing youngstock separately from cows until pregnancy, and purchasing new animals were factors possibly related to a high occurrence of respiratory disease symptoms in pregnant heifers and cows. The highest risk of abortions (> 1.3%) and increased insemination index (number of inseminations per pregnancy) (> 1.9) occurred in herds with a moderate prevalence of BHV-1 antibodies (1-49%) in cows.
BHV-1 was not associated with acute respiratory disease in adult dairy cattle, however was significantly related to reproductive performance. BRSV possesses the main role in respiratory disease complex in adult dairy cattle.
Bovine respiratory disease; reproduction; dairy cattle; bovine herpesvirus 1; bovine respiratory syncytial virus
Abortions occurred in 18% of 131 beef cows and heifers during two months, on a farm in southern Saskatchewan. The losses began two weeks after acute febrile illness and agalactia in a dairy cow to which the beef herd had been exposed. A diagnosis of Leptospira interrogans serovar pomona infection was made on the basis of serology in cows and the finding of leptospires in fetal tissues by fluorescent antibody test. Tentative diagnosis of infectious bovine rhinotracheitis delayed treatment and prophylaxis until infection attained high intensity in the herd and severe losses to the farmer occurred. Abortions ceased after vaccination against pomona and oxytetracycline treatment of pregnant cows, although chronic debility followed the acute phase of the disease in some cows. Recrudescence of infection was suspected four months later, when acute agalactia occurred in one cow and debility in calves and cows was recurring. Pomona infection was not proven, but dihydrostreptomycin treatment and revaccination were applied to the whole herd. Seroconversion and IgM antibody continued to indicate a persistent source of infection and susceptibility in a minority of the population one year after onset. The source of the original infection is believed to have been a carrier beef cow, or a dairy cow which was leptospiruric at the time of contact with the beef herd. With the exception of one aborted calf, no evidence of pomona infection was found outside the farm, in cattle or wild mammals tested serologically within a radius of 30 km, during one year following the outbreak.
Abortion; bovine; pomona; leptospirosis
Stable mycoplasma antigens for the indirect hemagglutination test (IHA) were prepared employing glutaraldehyde treated sheep erythrocytes sensitized with Mycoplasma agalactiae subsp. bovis and Mycoplasma bovigenitalium antigens. Employing these antigens mycoplasma antibodies were detected in sera from cattle which had mastitic symptoms due to natural infection with either M. agalactiae subsp. bovis or M. bovigenitalium. A total of 200 cows from four herds were examined at varying intervals for the presence of M. agalactiae subsp. bovis and for the detection of antibody using growth inhibition and IHA tests. Mycoplasmas were isolated from 37 animals. Growth inhibiting antibody was detected from 56 of the 200 animals. In the IHA tests, antibody titer greater than or equal to 1:80 were detected in 148 animals, 76 of these having antibody titers greater than or equal to 1:160, while sera of 116 normal control animals had no growth inhibiting antibody and none had IHA antibody titers greater than 1:40. M. bovigenitalium was isolated from the milk of three of 26 animals in a fifth herd during an outbreak of mastitis. Growth inhibiting antibodies were demonstrated in the sera of ten of the 26 animals. However, the IHA test detected antibody titers of greater than or equal to 1:160 in 13 animals and of 1:80 in one of the 26 animals. To determine the specificity of the IHA tests, M. agalactiae subsp. bovis and M. bovigenitalium antigens were reacted with rabbit hyperimmune typing sera produced against 12 species of bovine mycoplasmatales. Homologous antisera showed IHA antibody titers of 1:1280 and 1:2560 against M. agalactiae subsp. bovis and M. bovigenitalium respectively, whereas heterologous antisera showed IHA antibody titers of less than or equal to 1:20. Also eight type-specific bovine antisera were reacted with M agalactiae subsp. bovis and M. bovigenitalium antigens in homologous and heterologous tests. Homoogous reactions showed IHA antibody titers greater than or equal to 1:320, whereas heterologous reactions showed IHA titers of less than or equal to 1:20. This IHA test promises to be useful for the detection of bovine mycoplasma antibodies in sera from cattle infected with M. agalactiae subsp. bovis or M. bovigenitalium. Thes test is sensitive, reproducible and specific and the technique is relatively simple and rapid. The antigens were stable for at least seven months.
Pulsed-field gel electrophoresis and antimicrobial sensitivity testing were used as tools to investigate the epidemiology of Streptococcus uberis mastitis in dairy cows. A total of 62 different strains were found among 138 isolates from the four herds investigated, and between 10 and 26 different strains were found in each herd. There was no strain common to all four herds. Identical strains of S. uberis were detected from different quarters of individual cows and from cows within the same herd, suggesting that transmission from quarter to quarter and cow to cow had occurred. Despite the great variation in S. uberis strains, persistent infection with the same strain within a lactation was observed in most cows. Predominant strains were present in two herds. Preliminary investigations could not clarify why these particular strains might predominate, but in one herd there was a significant difference between the prevalence of clinical mastitis in quarters infected with the predominant strain and that in quarters infected with other strains, suggesting the greater virulence of the predominant strain. The wide variety of S. uberis strains found is consistent with an environmental source of S. uberis. However, evidence of direct transmission, the persistence of infection, and the predominance of particular strains in some herds indicate that S. uberis infections are epidemiologically complex and that the relative importance of these factors in the occurrence of mastitis may differ between herds.
A herd of 125 Holstein cows manifested fertility problems for two years. The number of services per pregnancy was 2.97, conception rate was 33% after the first service, and the average number of open days was 127. Abortions occurred in four cows over the last 12 months. The herd was not vaccinated against any disease. Natural service by a bull and artificial insemination were used for breeding the cows. Bovine herpesvirus type 1 was demonstrated in sperm heads from the bull by direct and indirect fluorescent antibody techniques, and the virus was isolated on cell cultures. The virus was also isolated from the uterine secretions of some cows and from two aborted fetuses.
The prevalence and antimicrobial susceptibilities of Campylobacter spp. isolates from bovine feces were compared between organic and conventional dairy herds. Thirty organic dairy herds, where antimicrobials are rarely used for calves and never used for cows, were compared with 30 neighboring conventional dairy farms, where antimicrobials were routinely used for animals for all ages. Fecal specimens from 10 cows and 10 calves on 120 farm visits yielded 332 Campylobacter isolates. The prevalence of Campylobacter spp. in organic and conventional farms was 26.7 and 29.1%, and the prevalence was not statistically different between the two types of farms. Campylobacter prevalence was significantly higher in March than in September, higher in calves than in cows, and higher in smaller farms than in large farms. The rates of retained placenta, pneumonia, mastitis, and abortion were associated with the proportion of Campylobacter isolation from fecal samples. The gradient disk diffusion MIC method (Etest) was used for testing susceptibility to four antimicrobial agents: ciprofloxacin, gentamicin, erythromycin, and tetracycline. Two isolates were resistant to ciprofloxacin, and none of isolates was resistant to gentamicin or erythromycin. Resistance to tetracycline was 45% (148 of 332 isolates). Tetracycline resistance was found more frequently in calves than in cows (P = 0.042), but no difference was observed between organic and conventional farms. When we used Campylobacter spp. as indicator bacteria, we saw no evidence that restriction of antimicrobial use on dairy farms was associated with prevalence of resistance to ciprofloxacin, gentamicin, erythromycin, and tetracycline.
In order to characterize the humoral and cellular immune responses to bovine mammary protothecosis, serum and whey samples obtained from 72 dairy cows assigned to four different clinical stages of infection were examined for specific antibodies by indirect enzyme-linked immunosorbent assay techniques. Milk samples were analyzed for the total numbers of excreted algal cells and somatic cells. After characterization of the course of immune induction in bovine protothecal mastitis, a long-term sentinel study was performed in an affected herd in order to investigate disease progression. A total of 61 dairy cows with protothecal mastitis were examined for shedding of algae cells and for local immune responses three times in 6-month intervals. During acute and chronic stages of protothecosis, significantly elevated specific antibody activities in sera were detected. A strong correlation of whey immunoglobulin A (IgA) and whey IgG1 antibody activity with the total counts of somatic cells in milk was observed, whereas only a weak correlation of whey IgA and whey IgG1 concentrations to the number of algal cells excreted with the milk was seen. Our results from the sentinel long-term study of infected cows revealed that 70.5% of the persistently infected animals were continuously shedding the pathogen. About 4.9% of the animals showed an intermittent shedding, whereas 18% of the cows were tested culturally negative throughout the study. It can be assumed that Prototheca zopfii mastitis in dairy cows is maintained on the herd level by subclinically infected alga-shedding cows.
Salmonella enteritidis phagetype 8 was isolated from ill humans, milk-line filters, milk from a bulk tank, and milk from the right hind quarter of a five-year-old Holstein cow on a dairy farm in southern Alberta. The affected animal was removed from the herd and continued to shed S. enteritidis from this quarter during a seven-month interval in an isolation facility. Milk from the affected quarter was visually normal, and no other pathogen was isolated from the udder during the investigation. After removal of the infected cow from the herd, milk from the bulk tank was culturally negative for Salmonella sp. during the succeeding 15 months.