Recent insights into the mucosal reactions associated with Giardia lamblia infections.

Giardia lamblia is an intestinal protozoan parasite infecting humans and various other mammalian hosts. The most important clinical signs of giardiasis are diarrhoea and malabsorption. Giardia lamblia is able to undergo continuous antigenic variation of its major surface antigen, named VSP (variant surface protein). While intestinal antibodies, and more specifically anti-VSP IgA antibodies, were proven to be involved in modulating antigenic variation of the parasite the participation of the local antibody response in control of the parasite infection is still controversial. Conversely, previous studies based on experimental infections in mice showed that cellular immune mechanisms are essential for elimination of the parasite from its intestinal habitat. Furthermore, recent data indicated that inflammatory mast cells have a potential to directly, or indirectly, interfere in duodenal growth of G. lamblia trophozoites. However, this finding was challenged by other reports, which did not find a correlation between intestinal inflammation and resistance to infection. Since intestinal infiltration of inflammatory cells and/or CD8+T-cells were demonstrated to coincide with villus-shortening and crypt hyperplasia immunological reactions were considered to be a potential factor of pathogenesis in giardiasis. The contribution of physiological factors to pathogenesis was essentially assessed in vitro by co-cultivation of G. lamblia trophozoites with epithelial cell lines. By using this in vitro model, molecular (through surface lectins) and mechanical (through ventral disk) adhesion of trophozoites to the epithelium was shown to be crucial for increased epithelial permeability. This phenomenon as well as other Giardia-induced intestinal abnormalities such as loss of intestinal brush border surface area, villus flattening, inhibition of disaccharidase activities, and eventually also overgrowth of the enteric bacterial flora seem to be involved in the pathophysiology of giardiasis. However, it remains to be elucidated whether at least part of these pathological effects are causatively linked to the clinical manifestation of the disease.

The influence of the rearing period on intramammary infections in Swiss dairy heifers: A cross-sectional study

Healthy replacement heifers are one of the foundations of a healthy dairy herd. Farm management andrearing systems in Switzerland provide a wide variety of factors that could potentially be associated withintramammary infections (IMI) in early lactating dairy heifers. In this study, IMI with minor mastitispathogens such as coagulase-negative staphylococci (CNS), contagious pathogens, and environmentalmajor pathogens were identified. Fifty-four dairy farms were enrolled in the study. A questionnaire wasused to collect herd level data on housing, management and welfare of young stock during farm isitsand interviews with the farmers. Cow-level data such as breed, age at first calving, udder condition andswelling, and calving ease were also recorded. Data was also collected about young stock that spent aperiod of at least 3 months on an external rearing farm or on a seasonal alpine farm. At the quarterlevel, teat conditions such as teat lesions, teat dysfunction, presence of a papilloma and teat lengthwere recorded. Within 24 h after parturition, samples of colostral milk from 1564 quarters (391 heifers)were collected aseptically for bacterial culture. Positive bacteriological culture results were found in 49%of quarter samples. Potential risk factors for IMI were identified at the quarter, animal and herd levelusing multivariable and multilevel logistic regression analysis. At the herd level tie-stalls, and at cow-level the breed category “Brown cattle” were risk factors for IMI caused by contagious major pathogenssuch as Staphylococcus aureus (S. aureus). At the quarter-level, teat swelling and teat lesions were highlyassociated with IMI caused by environmental major pathogens. At the herd level heifer rearing at externalfarms was associated with less IMI caused by major environmental pathogens. Keeping pregnant heifersin a separate group was negatively associated with IMI caused by CNS. The odds of IMI with coagulase-negative staphylococci increased if weaning age was less than 4 months and if concentrates were fed tocalves younger than 2 weeks. This study identified herd, cow- and quarter-level risk factors that may beimportant for IMI prevention in the future.