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Pathogens may gain a fitness advantage through manipulation of the behaviour of their hosts. Likewise, host behavioural changes can be a defence mechanism, counteracting the impact of pathogens on host fitness. We apply harmonic radar technology to characterize the impact of an emerging pathogen--Nosema ceranae (Microsporidia)--on honeybee (Apis mellifera) flight and orientation performance in the field. Honeybees are the most important commercial pollinators. Emerging diseases have been proposed to play a prominent role in colony decline, partly through sub-lethal behavioural manipulation of their hosts. We found that homing success was significantly reduced in diseased (65.8%) versus healthy foragers (92.5%). Although lost bees had significantly reduced continuous flight times and prolonged resting times, other flight characteristics and navigational abilities showed no significant difference between infected and non-infected bees. Our results suggest that infected bees express normal flight characteristics but are constrained in their homing ability, potentially compromising the colony by reducing its resource inputs, but also counteracting the intra-colony spread of infection. We provide the first high-resolution analysis of sub-lethal effects of an emerging disease on insect flight behaviour. The potential causes and the implications for both host and parasite are discussed.

Western honey bees ( Apis mellifera ) face an increasing number of challenges that in recent years have led to significant economic effects on apiculture, with attendant consequences for agriculture. Nosemosis is a fungal infection of honey bees caused by either Nosema apis or N. ceranae . The putative greater virulence of N. ceranae has spurred interest in understanding how it differs from N. apis . Little is known of effects of N. apis or N. ceranae on honey bee learning and memory. Following a Pavlovian model that relies on the proboscis extension reflex, we compared acquisition learning and long-term memory recall of uninfected (control) honey bees versus those inoculated with N. apis , N. ceranae , or both. We also tested whether spore intensity was associated with variation in learning and memory. Neither learning nor memory differed among treatments. There was no evidence of a relationship between spore intensity and learning, and only limited evidence of a negative effect on memory; this occurred only in the co-inoculation treatment. Our results suggest that if Nosema spp. are contributing to unusually high colony losses in recent years, the mechanism by which they may affect honey bees is probably not related to effects on learning or memory, at least as assessed by the proboscis extension reflex.

BACKGROUND Diarrhoea in AIDS is associated with anorexia and weight loss. The importance of gastrointestinal transit in such symptoms has not been addressed. AIMS To assess jejunal to caecal transit times in subjects with AIDS related diarrhoea and weight loss and correlate these with measures of absorptive capacity and intestinal permeability. METHODS Jejunal to caecal transit times were assessed in 20 seronegative controls and 60 HIV seropositive subjects from serum analysis of 3-O-methyl-d-glucose and sulphapyridine after ingestion of the monosaccharide and sulphasalazine in aqueous solution. The method also allows an estimation of gastric emptying times for liquids. Intestinal absorptive capacity and permeability were assessed by a combined test using 3-O-methyl-d-glucose, d-xylose,l-rhamnose, and lactulose. RESULTS Gastric emptying was significantly delayed in all groups of patients with AIDS. Mean jejunal to caecal transit times were not significantly different between controls (246 (62) minutes) and patients without diarrhoea (AIDS, well: 278 (103) minutes; AIDS, wasting: 236 (68) minutes), cytomegalovirus colitis (289 (83) minutes), pathogen negative diarrhoea (192 (100) minutes), or microsporidiosis (190 (113) minutes), although 30% of patients had values below the control range. Patients with cryptosporidiosis differed significantly from controls (135 (35) minutes, p<0.0001), seven of 10 having rapid transit times. Absorptive capacity was reduced and intestinal permeability significantly increased in AIDS, but did not correlate significantly with transit times. CONCLUSION Small bowel transit is accelerated in many patients with AIDS, particularily in protozoal diarrhoea, but is not the sole explanation for malabsorption of monosaccharides.

It has been proposed that parasitic infections increase selection against inbred genotypes. We tested this hypothesis experimentally using pairs of selfed and outcrossed sibling lines of the freshwater crustacean Daphnia magna, which can be maintained clonally. We studied the performance of selfed relative to outcrossed sibling clones during repeated pairwise clonal competition in the presence and absence of two species of microsporidian parasites. In 13 of the 14 pairs, the selfed clones did worse than the outcrossed ones in the control treatment, but the presence of either parasite did not result in an overall increase in this difference. Rather, it decreased the performance of the selfed relative to the outcrossed sibling in some pairs and increased it in others. Moreover, the two parasite species did not have the same effect in a given pair. This indicates that, contrary to the hypothesis that parasites generally lead to a decreased performance of inbred genotypes, their effect may depend on the genetic background of the host as well as on the parasite species, and suggests that inbreeding can lead to reduced or increased resistance to parasites. Our findings also indicate that there is variation for specific resistance to different species of parasites in the metapopulation from which the hosts for this study were obtained.

A study was conducted to determine the prevalence, geographical distribution, and effects of a microsporan parasite, Loma branchialis, in Atlantic cod in coastal Newfoundland. The parasite was identified microscopically as opaque, ovoid xenomas, primarily in the gills, heart, and spleen. Although widely distributed in young fish inhabiting 7 coastal localities, prevalence was 1–7% in general, <0.01% in older and large fish, but 78% in market-size cod from a commercial farm. Some of the latter fish were emaciated, and ∼2 mo after the parasite was detected, 63% succumbed with a massive infection. Condition factor and blood values were significantly lower than those in reference fish. An experimental study conducted over 2 yr revealed that mass gained and condition factor were significantly lower in infected cod than in controls at the termination of the study. Feed consumption, mass gained, feed conversion efficiency, and condition factor also were significantly lower in another group of infected cod of marketable size studied over 12 wk. Xenomas also were observed in the heart and gills of year class II cod reared in a hatchery. Loma branchialis is considered to be a potential pathogen in both hatchery-reared and net pen–cultured cod in Newfoundland.

The prevalence of intestinal microsporidiosis among human immunodefiency virus (HIV)-infected persons with chronic diarrhea varies from 7% to 50%; thus, microsporidia are a significant source of morbidity and, occasionally, mortality among these patients. Anecdotal reports suggest that intestinal microsporidiosis is also an important infection in patients with AIDS in Germany. To determine the prevalence of microsporidiosis among HIV-infected patients in Germany, we performed a prospective coprodiagnostic study of 97 consecutive HIV-infected patients. Microsporidia were the most common enteropathogen identified in 18 (36.0%) of 50 patients with diarrhea and 2 (4.3%) of 47 patients without diarrhea (P < .001; χ2 test). Microsporidia were present in 60% of patients with chronic diarrhea and 5.9% of patients with acute diarrhea. The etiologic agent was Enterocytozoon bieneusi in 18 patients and Encephalitozoon intestinalis in two patients. The prevalence of intestinal microsporidiosis in this cohort of German patients with AIDS and diarrhea is one of the highest to be reported anywhere in the world. Microsporidiosis seems to represent one of the most important causes of diarrhea in HIV-infected patients in Germany and thus must be considered in the differential diagnosis for all AIDS patients presenting with diarrhea.

Brachiola algerae (Vavra et Undeen, 1970) Lowman, Takvorian et Cali, 2000, originally isolated from a mosquito, has been maintained in rabbit kidney cells at 29 degrees C in our laboratory. This culture system has made it possible to study detailed aspects of its development, including spore activation, polar tube extrusion, and the transfer of the infective sporoplasm. Employing techniques to ultrastructurally process and observe parasite activity in situ without disturbance of the cultures has provided details of the early developmental activities of B. algerae during timed intervals ranging from 5 min to 48 h. Activated and nonactivated spores could be differentiated by morphological changes including the position and arrangement of the polar filament and its internal structure. The majority of spores extruded polar tubes and associated sporoplasms within 5 min post inoculation (p.i.). The multilayered interlaced network (MIN) was present in extracellular sporoplasms and appeared morphologically similar to those observed in germination buffer. Sporoplasms, observed inside host cells were ovoid, contained diplokaryotic nuclei, vesicles reminiscent of the MIN remnants, and their plasmalemma was already electron-dense with the \"blister-like\" structures, typical of B. algerae. By 15 min p.i., the first indication of parasite cell commitment to division was the presence of chromatin condensation within the diplokaryotic nuclei, cytoplasmic vesicular remnants of the MIN were still present in some parasites, and early signs of appendage formation were present. At 30 min p.i., cell division was observed, appendages became more apparent, and some MIN remnants were still present. By two hours p.i., the appendages became more elaborate and branching, and often connected parasite cells to each other. In addition to multiplication of the organisms, changes in parasite morphology from small oval cells to larger elongated \"more typical\" parasite cells were observed from 5 h through 36 h p.i. Multiplication of proliferative organisms continued and sporogony was well underway by 48 h p.i., producing sporonts and sporoblasts, but not spores. The observation of early or new infections in cell cultures 12-48 h p.i., suggests that there may also exist a population of spores that do not immediately discharge, but remain viable for some period of time. In addition, phagocytized spores were observed with extruded polar tubes in both the host cytoplasm and the extracellular space, suggesting another means of sporoplasm survival. Finally, extracellular discharged sporoplasms tightly abutted to the host plasmalemma, appeared to be in the process of being incorporated into the host cytoplasm by phagocytosis and/or endocytosis. These observations support the possibility of additional methods of microsporidian entry into host cells and will be discussed.

In recent years the microsporidial species Enterocytozoon bieneusi has been reported to be pathogenic in multiple cases of AIDS-related cholangitis. We describe a patient with AIDS who developed a case of acalculous cholecystitis in which E. bieneusi was the only identifiable pathogen. A 37-year-old male with no significant medical history and no reported risk factors for HIV infection presented to the University of Massachusetts Medical Center (Worcester, MA) with a 6-month history of watery diarrhea. He also had persistent pain in the right upper quadrant and reported a weight loss of 42 pounds. He was found to be seropositive for HIV and to have a CD4 super(+) cell count of 130/mm super(3). A sphincterotomy was performed, and cultures of the aspirated bile revealed the presence of microsporidia organisms with no evidence of CMV, Cryptosporidium species, or other pathogens. Following the procedure the patient's right upper-quadrant pain and fever resolved. Several months later he was readmitted to the hospital with a fever of 39 degree C, nausea, vomiting, diarrhea, and worsening tenderness in the right upper quadrant. A laparoscopic cholecystectomy was performed, and pathological examination of the gallbladder revealed inflammatory changes consistent with chronic acalculous cholecystitis and diffuse intracellular microsporidia organisms. At a 10-month follow-up examination, the patient remained free of right upper-quadrant pain.

Background In September 2008, a disease outbreak characterized by acute, severe gill pathology and peritonitis, involving the gastrointestinal tract, was observed in an Atlantic salmon ( Salmo salar L.) farm in north-western Norway. During subsequent sampling in November 2008 and January 2009, chronic proliferative gill inflammation and peritonitis was observed. Cumulative mortalities of 5.6–12.8% and severe growth retardation were observed. Routine diagnostic analysis revealed no diseases known to salmon at the time, but microsporidian infection of tissues was observed. Methods To characterize the disease outbreak, a combination of histopathology, in situ hybridization (ISH), chitin, calcofluor-white (CFW) staining, and real-time PCR were used to describe the disease progression with visualization of the D. lepeophtherii stages in situ. Results The presence of the microsporidian Desmozoon lepeophtherii was confirmed with real-time PCR, DNA sequencing and ISH, and the parasite was detected in association with acute lesions in the gills and peritoneum. ISH using a probe specific to small subunit 16S rRNA gene provided an effective tool for demonstrating the distribution of D. lepeophtherii in the tissue. Infection in the peritoneum seemed localized in and around pre-existing vaccine granulomas, and in the gastrointestinal walls. In the heart, kidney and spleen, the infection was most often associated with mononuclear leucocytes and macrophages, including melanomacrophages. Desmozoon lepeophtherii exospores were found in the nuclei of the gastrointestinal epithelium for the first time, suggesting a role of the gastrointestinal tract in the spread of spores to the environment. Conclusions This study describes the progression of D. lepeophtherii disease outbreak in an Atlantic salmon farm without any other known diseases present. Using different methods to examine the disease outbreak, new insight into the pathology of D. lepeophtherii was obtained. The parasite was localized in situ in association with severe tissue damage and inflammation in the gills, peritoneal cavity and in the gastrointestinal (GI) tract that links the parasite directly to the observed pathology.