Outbreak of Pseudomonas aeruginosa mastitis in a dairy cow herd in northern Greece and its control with an autogenous vaccine.

In a dairy cow herd consisted of herd of 200 lactating Holstein-Friesian cows and heifers, clinical signs of mastitis in 40 out of 170 animals were observed. Treatments with antibiotics were proved ineffective. Milk bacterial cultures from 15 affected animals revealed Pseudomonas aeruginosa. An autogenous vaccine was administered subcutaneously, twice in a month period, to all adults. Cases of clinical mastitis declined significantly (p⟨0.0001) during next 3 months.

Gastrointestinal trichostrongylosis can predispose ewes to clinical mastitis after experimental mammary infection.

Objective was to study, in an experimental model, the possible role of gastrointestinal nematode infection in predisposing ewes to mastitis during the lactation period. Twenty-four ewes (A or B [n=12]), free from nematode and trematode helminths, were used. Group A animals received 5000 third-stage larvae of a trichostrongylid helminth cocktail and group B ewes were unparasitised controls. Animals in group A developed gastrointestinal trichostrongylosis confirmed by >500epg in faecal samples; mean epg of group B ewes were <20 (P<0.001). Ewes were challenged by deposition of Mannheimia haemolytica into the teat duct. In group A, 7 ewes developed clinical and 5 subclinical mastitis; no ewe in group B developed clinical mastitis, but only subclinical (12 ewes) (P=0.002). M. haemolytica was isolated from 132/132 and 121/132 udder samples from group A or B, respectively (P<0.015); increased leucocyte numbers were recorded in 66/66 and 61/66 samples, respectively (P=0.023). During post-mortem examination, mean number of helminths in gastrointestinal content was 2523 and 7.5 in group A or B, respectively (P<0.001); within group A, proportions of Teladorsagia and Haemonchus were significantly greater in ewes that developed clinical mastitis than in others which did not (0.709 and 0.162 versus 0.662 and 0.136, respectively; P<0.035). M. haemolytica was isolated from 36/36 and 19/36 udder tissue samples from group A or B, respectively (P<0.001). In ewes with subclinical mastitis (in group A or B), inducible-lymphoid-follicles were observed in the teat, which were not observed in ewes with clinical disease. Total pathology scores summed over all days were 127 and 73 for group A or B ewes, respectively (maximum possible 192; P<0.05). In general, there was positive correlation between intestinal helminth counts and pathology score (P<0.001) and between Teladorsagia counts and pathology score (P=0.002) in ewes that developed clinical mastitis. It is concluded that, in view of bacterial challenge, gastrointestinal trichostrongylosis and particularly Teladorsagia infection, might lead to clinical mastitis, through various pathogenetic pathways.

Health management of ewes during pregnancy.

The objectives of health management of ewes during pregnancy are as follows: (i) successful completion of pregnancy at term, (ii) birth of healthy and viable lambs, with optimal birth and potential weaning bodyweight, (iii) optimum milk production during the subsequent lactation and (iv) improved management in relation to drug residues in animal products. Knowledge of the physiological background of pregnancy in ewes: changes, mechanisms and interactions, during pregnancy is important for the overall health management of ewes during pregnancy. Health management of pregnant ewes includes diagnosis of pregnancy and evaluation of the number of foetuses borne, which will support strategies for subsequent management of the flock. Nutritional management of ewes depends upon the stage of lactation and specifically aims to (i) prevention of pregnancy toxaemia and other metabolic diseases during the peri-partum period, (ii) formation of colostrum in appropriate quantity and quality, (iii) production of lambs with normal future birth bodyweight and (iv) support of increased milk yield during the subsequent lactation. At the end of lactation, udder management of pregnant ewes includes its clinical examination, culling of ewes considered unsuitable for lactation and, possibly, the intramammary administration of antibiotics; objectives of that procedure are (i) to cure infections which have occurred during the previous lactation and (ii) to prevent development of new mammary infection during the dry period. Management of abortions includes the correct and timely diagnosis of the causative agent of the disorder, as well as the strategic administrations of chemotherapeutic agents, aiming to prevent abortions in flocks with confirmed infection with an abortifacient agent, especially if no appropriate vaccinations had been carried out before the mating season. During the final stage of pregnancy, health management of ewes includes administration of appropriate anthelmintic drugs, aiming to eliminate gastrointestinal helminthes (thus, increasing production output of ewes) and preventing the built-up of parasitic burdens in the environment (thus, reducing infection of lambs during their neonatal period). Vaccinations of pregnant ewes aim to protect these animals, as well as their offspring, especially against diseases which are a frequent cause of neonatal mortality (e.g., clostridial infections). Health management also aims to prevent the main metabolic disorders of pregnant ewes (i.e., pregnancy toxaemia and hypocalcaemia), as well as to monitor flocks for development of these disorders. Health management of pregnant ewes is completed with application of husbandry practices before the start of the lambing season. Finally, in some cases, health management may include induction and synchronisation of lambings, which is a management or therapeutic procedure.

Transmission of Mannheimia haemolytica from the tonsils of lambs to the teat of ewes during sucking.

Objective of the work was to study whether Mannheimia haemolytica may be transmitted from the mouth of the lambs into the teat of the dam during sucking. We compared bacterial populations within the teat duct and milk of ewes immediately before and immediately after sucking by the lambs. Tonsils of lambs of the ewes were swabbed. M. haemolytica strain DAG21T recovered from a teat duct of a ewe was compared to strain DAG21R recovered from the tonsils of her lamb by using 16s rRNA sequencing. We used those two isolates and another one of known pathogenicity, for challenging ewes: (i) 2 mm deep into healthy teats, (ii) 2 mm deep into teats with chapping lesions or (iii) into the cistern of healthy mammary glands. Of samples collected before suckling, 20/792 were bacteriologically positive, and of those after, 50/792 were bacteriologically positive (P<0.001); in 37 cases, a negative sample became positive. One M. haemolytica (DAG21T) was recovered after suckling from a teat duct of a ewe. The organism was isolated from 57/90 tonsillar swabs from lambs. Risk of infection of ewe' teats was 0.004 throughout lactation, being greatest (0.021) during the 3rd week of lactation. The 16s rRNA sequences of strains DAG21T and DAG21R were identical over 1450 nucleotides. Phylogenetic analysis showed that the two isolates clustered together with isolates of M. haemolytica. Organism deposition into healthy teats caused subclinical mastitis; deposition into teats with lesions or directly into mammary gland caused clinical mastitis. When results of inoculation of the three strains were compared between them, statistical significance was always P>0.9. Results provide clear evidence that suckling by lambs can lead to transmission of M. haemolytica into the teats of the ewes; the bacteria have the potential to cause mastitis if circumstances are favourable.

Administration of a long-acting antiparasitic to pre-pubertal ewe-lambs in Greece results in earlier reproductive activity and improved reproductive performance.

We studied the reproductive effects of administration of a long-acting antiparasitic (moxidectin) given to pre-pubertal ewe-lambs in Greece at the beginning of the reproductive season. 45 animals, naturally infected with trichostrongylids, were allocated into treated (n=30, treatment on D0, 21 June) or control (n=15) group. Rams of confirmed fertility, were introduced from 15 August (D55) to 20 December (D182) into the ewe-lambs. Throughout the study (performed at latitude N 36°26', in a flock free from brucellosis, Chlamydophila infection and toxoplasmosis), epg counts were monitored and reproductive performance of ewes was assessed. Up to D112, arithmetic mean epg counts in treated animals were 0; thereafter and up to D350, they were 23-473. Respective figures for controls were 190-977 epg. Reproductive performance parameters for treated and control animals respectively, were as follows; median 'Interval to first mating after ram introduction': 36.5 d and 71.0 (P=0.04); median 'Age at first mating': 8.5m and 10.0m (P=0.045); 'Cycling rate': 20.0% and 6.7% (P=0.03); 'Mating rate': 86.7% and 66.7%; 'Return-to-oestrus rate': 26.7% and 26.7%; 'Abortion rate': 3.3% and 0%; 'Lambing rate': 83.3% and 66.7%; 'Total lambs born per ewe' and 'Liveborn lambs born per ewe': 1.5 and 1.1 (P=0.01); 'Stillbirth rate' 0% and 0% and 'Lamb bodyweight per ewe': 5.0 kg and 3.8 kg (P=0.005). Anthelmintic treatment of pre-pubertal ewes, in order to maximise reproductive performance may be employed as a management strategy according to targets set in individual flocks.

The induction of lymphoid follicle-like structures in the ovine teat duct following experimental infection with Mannheimia haemolytica.

The objectives of this study were to investigate the early stages of experimental infection of the ovine mammary gland with Mannheimia haemolytica and to identify the lymphocyte subsets accumulating at the teat duct. M. haemolytica was inoculated into one teat of each of 25 ewes and clinical, bacteriological, cytological, haematological, physicochemical, gross pathological, histopathological and immunohistochemical examinations were carried out. Clinical signs of inflammation were evident by 8 h but had subsided 2 days after challenge. Polymorphonuclear neutrophils (PMN) predominated in milk films up to 1 day following challenge, but the proportion of lymphocytes and macrophages progressively increased thereafter. Total blood leucocyte counts decreased immediately after challenge and then rose until 1 day after challenge with immature PMNs comprising >3% of the total. The pH of the mammary secretions from the challenged side was increased (>7.0). Focal lymphoid accumulations were observed in the lamina propria at the junction of the teat duct and cistern, including CD79(+), CD3(+) and gammadelta T cells, CD68(+) and MHC-II(+) cells with a particular increase in the numbers of CD8(+) T cells from days 3 to 5 after challenge. The findings suggest that these organised lymphoid structures are inducible and contribute to the defence of the infected teat when the PMN-macrophage response is overwhelmed.

Post-partum involution of the canine uterus - gross anatomical and histological features.

We aimed to study the normal puerperium in the bitch. Ovariohysterectomy was performed in nine bitches, each at a different day after normal whelping; their genital tract was subject to gross anatomical examination, as well as to histological examination and electron microscopy scanning. Corpora albicans were evenly distributed in the left and right ovaries and placental sites were evenly distributed among left and right uterine horns. Placental sites were initially of dark green to grey colour, later becoming dark brown; their length and height progressively decreased. Height of the myometrium and diameter of the uterine glands progressively decreased. Trophoblast-like cells were consistently observed at the placental sites and on the surface of the interplacental areas, at all time points where hysterectomy had been performed. It is suggested that involution of the canine genital tract can last up to 3 months and is slow. Continuous (up to D84 post-partum) presence of prominent placental sites should be considered a normal feature of canine uterine post-partum involution.

Teat lesions predispose to invasion of the ovine mammary gland by Mannheimia haemolytica.

Teat lesions, produced in ewes by an experimental chapping procedure, were found to facilitate experimental infection with Mannheimia haemolytica, as assessed by observations on infection of the teat skin, teat duct and mammary gland, and on the production of mastitis. The origin of the M. haemolytica strain used (ovine tonsillar or mammary infection) did not appear to influence the results. In a second experiment, in which ewes continued to suckle their lambs but were not deliberately infected, chapping was shown to favour infection by Staphylococcus epidermidis, Staphylococcus aureus and M. haemolytica.

Experimental staphylococcal mastitis in bitches: clinical, bacteriological, cytological, haematological and pathological features.

The objectives of the work were to study the features of experimentally induced canine mastitis and to present hypotheses regarding the pathogenesis of the disease. The right caudal abdominal mammary gland of six bitches was inoculated on day 8 after whelping with Staphylococcus intermedius to induce mastitis; adjacent mammary glands were used as controls. Clinical examination, bacteriological and cytological (whiteside test, Giemsa) examination of mammary secretion, as well as haematological tests were performed from 5 days before until 34 days after challenge. Mastectomy was sequentially performed 1, 2, 4, 18, 26 and 34 days after challenge in each of the bitches, in order to carry out a pathological examination of mammary glands. All animals developed clinical mastitis: challenged glands became painful, hot, enlarged and oedematous; secretion was brownish, purulent, with flakes or clots, subsequently becoming yellowish and thick. Staphylococci were isolated from all inoculated glands (up to 22 days). WST was positive in 41/46 samples from inoculated glands and 66/138 samples from control glands; neutrophils predominated during the acute stage. Blood leukocyte counts increased, whilst platelet counts decreased. Gross pathological findings initially included congestion, purulent discharge and subcutaneous oedema; then abscesses, brownish areas and size decrease were seen. Salient histopathological features were initially neutrophilic infiltration, haemorrhages, destruction of mammary epithelial cells and alveoli, and then infiltration by lymphocytes, shrunken alveoli, loss of glandular architecture and fibrous tissue proliferation. We conclude that in bitches, intrammamary inoculation of Staphylococcus intermedius can induce clinical mastitis, followed by subclinical disease. The disorder is characterized by bacterial isolation and leukocyte influx in challenged glands, by leukocyte presence in adjacent mammary glands, by increased blood leukocyte counts and by destruction of mammary parenchyma.