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The effectiveness of copper oxide wire particles as an anthelmintic in pregnant ewes and safety to offspring.

The objective of the experiment was to determine the effectiveness of copper oxide wire particles (COWP) in pregnant ewes and safety to lambs. COWP have been used recently as an anthelmintic in small ruminants to overcome problems associated with nematode resistance to chemical dewormers. Doses of COWP (<or=4 g) have been used in lambs without clinical signs of copper toxicity. Use in pregnant ewes has not been examined. Mature Katahdin ewes were administered 0 (n=14), 2 (n=15), or 4 (n=15)g of COWP 33+/-1.6 days before lambing in late March 2004. Fecal egg counts (FEC) and blood packed cell volume (PCV) were determined between Days 0 (day of COWP administration) and 35. Lambs were weighed within 24h after birth, at 30 and 60 days of age, and in mid-September ( approximately 120 days of age). Blood was collected from lambs within 24h after birth and at 30 days of age for determination of the activity of the liver enzyme, aspartate aminotransferase (AST) in plasma. Within 7 days after COWP administration, FEC decreased by 1308 and 511 eggs/g (epg) in the 2 and 4 g groups, respectively, compared with an increase of 996 epg in the control group (P<0.02). PCV was similar among groups between Days 0 and 35. Lamb plasma AST activity at birth increased with increasing dose of COWP in dams (P<0.001). Plasma AST activity at 30 days of age was similar for lambs from ewes treated with 0 and 2g COWP, but was slightly greater in lambs from ewes treated with 4 g COWP (P<0.02). Birth weights decreased with increasing COWP (P<0.003). By 30 (COWPxbirth type, P<0.02) and 60 (COWPxbirth type, P<0.02) days of age, weight of multiple-born lambs decreased with increasing COWP, while weight of single-born lambs was similar among treatments. In mid-September ( approximately 120 days of age) weights of multiple-born lambs from ewes treated with 4 g COWP tended to be lightest compared with lambs from ewes treated with 0 or 2g COWP or single-born lambs (P<0.09). Lamb survival to 30, 60, or 120 days of age was not affected by COWP treatment to ewes. Administration of 4 g COWP to late pregnant ewes may negatively impact multiple-born offspring, but the 2g appears to be safe for production.

Animals↗

Evidence for localized bacterial loading as the cause of chronic beach closings in a freshwater marina.

We conducted a comprehensive regional spatial assessment of bacterial water quality in order to determine the points of entry of fecal pollution into a swimming beach area on Lake Michigan that historically has had numerous water quality advisories for elevated levels of Escherichia coli (E. coli). Intensive, consecutive-day water samples were collected during dry and rainy conditions across multiple shoreline and offshore sites, and E. coli levels were enumerated from these samples. For both dry and rainy days, shoreline sites demonstrated significantly higher E. coli levels than offshore regions. We found that offshore (10-150m from shore) E. coli levels did not exceed 235CFU/100ml in more than 5% of the samples collected for 19 surveys (n=209). In contrast, samples taken at the beach area exceeded 235CFU/100ml in 66% of the samples collected for 43 shoreline surveys (n=675). Locally high E. coli levels coincided with bird presence and stormwater at the swimming beach located within the marina, and were unrelated to E. coli levels in connecting harbor waters. We conclude that beach water quality may be impacted by local, persistent contamination, which may confound routine beach monitoring and prevent the detection of regional pollution from other sources.

Animals↗

Isolation of human faecal bifidobacteria which reduce signs of Salmonella infection when orogastrically dosed to mice.

AIMS: The aim of the study was to isolate human bifidobacteria that inhibit growth of Salmonella typhimurium in vitro, and provide protection against Salmonella infection in mice. METHODS AND RESULTS: A total of 92 micro-organisms, which displayed antagonist activity against Salm. typhimurium in vitro, were isolated from human faecal material. Based on their Gram stain status, cultures were pooled and tested for anti-Salmonella activity. The Gram-variable group was the most active. From that group, three bifidobacteria (Laftitrade markB22, B74 and B97) individually showed good pathogen inhibition in vivo. CONCLUSION: Oral administration of certain human bifidobacteria provides protection against Salmonella infection in mice. SIGNIFICANCE AND IMPACT OF THE STUDY: These results indicate that certain bifidobacteria may be used as a prophylaxis for reduced incidence and severity of Salmonella infections.

Animals↗

Treating irritable bowel syndrome with a food elimination diet followed by food challenge and probiotics.

OBJECTIVE: In Irritable Bowel Syndrome, the gut-associated immune system may be up-regulated resulting in immune complex production, low-grade inflammation, loss of Class I bacteria, and translocation of inflammatory mediators and macromolecules outside of the GI lumen. Since food intolerance may be one of the reasons for this upregulation, our goal was to investigate the role of food intolerance in IBS patients. METHODS: In this open label pilot study, we enrolled 20 patients with IBS by Rome II criteria (15 women, ages 24-81) who had failed standard medical therapies in a tertiary care GI clinic. Baseline serum IgE and IgG food and mold panels, and comprehensive stool analysis (CSA) were performed. Breath-hydrogen testing and IBS Quality-of-Life (QOL) questionnaires were obtained. Patients underwent food elimination diets based on the results of food and mold panels followed by controlled food challenge. Probiotics were also introduced. Repeat testing was performed at 6-months. We followed up with this cohort at 1 year after trial completion to assess the reported intervention and for placebo effect. RESULTS: Baseline abnormalities were identified on serum IgG food and mold panels in 100% of the study subjects with significant improvement after food elimination and rotation diet (p < 0.05). Significant improvements were seen in stool frequency (p < 0.05), pain (p < 0.05), and IBS-QOL scores (p < 0.0001). Imbalances of beneficial flora and dysbiotic flora were identified in 100% of subjects by CSA. There was a trend to improvement of beneficial flora after treatment but no change in dysbiotic flora. The 1-year follow up demonstrated significant continued adherence to the food rotation diet (4.00 +/- 1.45), minimal symptomatic problems with IBS (4.00 +/- 1.17), and perception of control over IBS (4.15 +/- 1.23). The continued use of probiotics was considered less helpful (3.40 +/- 1.60). CONCLUSION: These data demonstrate that identifying and appropriately addressing food sensitivity in IBS patients not previously responding to standard therapy results in a sustained clinical response and impacts on overall well being and quality of life in this challenging entity.

Adult↗

Nitrogen balance during recovery from secretory diarrhea of cholera in children.

This study describes nitrogen balance in children during recovery from severe cholera (bacteriologically confirmed). The subjects were six male children aged 12 to 24 months and weighing 6.29 to 9.86 kg (on recovery). They initially presented with dehydration and base deficit acidosis due to acute watery diarrhea. Nitrogen balance promptly improved with milk feeding even before diarrhea was fully controlled and irrespective of the clinical severity of the disease. There was no increase in stool volume and systemic acid base status remained unaffected when milk feeding was introduced. There was little nitrogen loss in the stool and the apparent absorption of protein was substantial. The negative nitrogen balance that occurred was largely due to the lack of intake. Early feeding and liberal intake appears to produce a more favorable impact than the cautious introduction of food. The common practice of restricting food during recovery from acute diarrhea is inappropriate in cholera.

Body Weight↗

A novel multiplex PCR assay for the detection of Salmonella enterica serovar Enteritidis in human faeces.

AIMS: To develop a multiplex PCR assay for the detection of Salmonella enterica serovar Enteritidis in human faeces. METHODS AND RESULTS: A total of 54 Salmonella strains representing 19 serovars and non-Salmonella strains representing 11 different genera were used. Five primer pairs were employed in the assay. Three of them targeted to the genes hilA, spvA and invA that encode virulence-associated factors. A fourth primer pair amplified a fragment of a unique sequence within S. enterica serovar Enteritidis genomes. An internal amplification control (a fragment of a conservative sequence within the 16S rRNA genes) was targeted by a fifth primer pair. The assay produced two or three amplicons from the invA, hilA and 16S rRNA genes for 19 Salmonella serovars. All Salmonella and non-Salmonella strains yielded a band of an internal amplification control. For S. enterica serovar Typhimurium, four products (the fourth from the spvA gene), and for S. enterica serovar Enteritidis five amplicons (the fifth from the sdf gene) were observed. S. enterica serovar Enteritidis was cultured from three of 71 rectal swabs from diarrhoeal patients. Five specific amplicons were generated with the multiplex PCR assay only from culture-positive faecal samples. CONCLUSION: The multiplex PCR assay specifically detects S. enterica serovar Enteritidis. SIGNIFICANCE AND IMPACT OF THE STUDY: This is a novel multiplex PCR assay, which contains an internal amplification control and enables concurrent survey for Salmonella virulence genes.

Feces↗

Effect of aspirin on protein binding and tissue disposition of oligonucleotide phosphorothioate in rats.

Pharmacokinetic studies of phosphorothioate oligodeoxynucleotides (PS-oligonucleotides) in animals show that following intravenous administration, PS-oligonucleotide clears out rapidly from the plasma and is distributed to majority of the organs. PS-oligonucleotides are bound to plasma proteins extensively. This study was aimed to determine the effect of aspirin, a commonly used drug, on pharmacokinetics of PS-oligonucleotides. In the present study, PS-oligonucleotide was administered to rats that had received aspirin by gavage. Pharmacokinetic study shows that if PS-oligonucleotide was administered following aspirin administration in rats, a) plasma pharmacokinetic parameters (t1/2alpha?, t1/2beta, AUC, etc.) had lower values, b) tissue disposition was different, and c) rate and route of elimination was affected in animals compared to rats receiving PS-oligonucleotide alone. This finding suggests that pharmacokinetics of PS-oligonucleotides can be affected with certain class of drugs, which may have direct impact on biological activity and safety.

Animals↗

Effects of dietary carbohydrates and buffering capacity on nutrient digestibility and manure characteristics in finishing pigs.

A 2 x 3 factorial experiment was conducted with 24 finishing pigs (Yorkshire x [Finnish Landrace x Dutch Landrace]) to determine the effects of dietary buffering capacity (BC) and carbohydrate sources on apparent total tract digestibility (TD), N retention, and manure characteristics. Twelve of these pigs were fitted with steered ileo-cecal value cannulas to measure the apparent ileal digestibility (ID) of N. Experimental variables were two levels of BC (High = 600 mEq/kg and Low = 530 mEq/kg) and three dietary carbohydrates (tapioca [28%], soybean hulls [25%], and sugar beet pulp [25%]). The two levels of BC were achieved by adjusting the amounts of alkalogenic limestone and acidogenic Ca sulfate in the diet. Pigs were fed twice daily at 2.4 x maintenance requirement for metabolizable energy (418 kJ ME/BW(0.75)). Chromic oxide was used as an indigestible marker. Feces and urine were collected over 5 d for nutrient balance and in vitro measurements of pH and ammonia emission over 7 d. No significant interactions between BC and dietary carbohydrates on the ID, TD, N retention, or manure characteristics were observed. Lowering BC with Ca sulfate did not affect digestibility of most nutrients, except for a negative impact on the TD of Ca (P = 0.015) and Mg (P = 0.003). Although all pigs receiving Ca sulfate had more acidic urine (by 0.49 pH units; P = 0.001), ammonia emission from manure was not lowered, irrespective of the carbohydrate source. Carbohydrates affected significantly the ID and TD of most nutrients, whereas N retention remained similar (P > 0.10). Urinary N:fecal N ratios in manure of pigs fed diets with tapioca, soybean hulls, and beet pulp were 2.09, 1.35, and 1.67, respectively. These ratios corresponded with in vitro ammonia emission (169, 125, and 148 mmol/7 d; P = 0.023). In conclusion, these results indicate that the acidification of urine in pigs fed Ca sulfate in the presence of NSP-rich carbohydrates was achieved. However, acidity of manure and ammonia emission were not affected. The addition of NSP from soybean hulls and(or) sugar beet pulp reduced ratios of urinary:fecal N, and thereby ammonia emission.

Acid-Base Equilibrium↗

Total and water-soluble phosphorus excretion from swine fed low-phytate soybeans.

A study was conducted to evaluate the impact of feeding soybean meal (SBM) from low-phytate (LP) or traditional phytate (TP) soybeans on performance and excretions from growing swine. Ninety-six crossbred barrows (initial BW = 18 +/- 0.3 kg) were allocated by BW to 24 pens and fed 1 of 4 treatment diets: TP SBM without supplemental phytase; TP SBM plus 500 phytase units of phytase/kg, as-fed basis [Ronozyme P (CT) 2500; DSM Nutritional Products, Basel, Switzerland]; LP SBM (USDA-ARS breeding line CX1834-1) without supplemental phytase, and LP SBM plus phytase. All diets within a feeding phase were formulated to be isocaloric and have similar available Lys and nonphytin P content. Pens were assigned randomly to treatments at the beginning of each of the 4 feeding phases. An indigestible marker was added to the mash feed. Individual pig weights and fecal samples were collected, and feed disappearance by pen was recorded weekly. No phytase inclusion or SBM source effects were observed for pen ADG, ADFI, or G:F (P > 0.05). Total tract apparent digestibility of DM and OM was not different among treatment groups (P > 0.05). Apparent digestibility of P was greater for pigs fed diets containing the LP SBM (48.9 vs. 42.4%; P < 0.01) and less when diets included phytase (44.3 vs. 47.0%; P < 0.0001). Total P (tP) and water-soluble P (WSP) excreted were affected by dietary treatment (tP: 20.0, 18.0, 16.8, and 13.8 g/kg of feces DM, P < 0.01; and WSP: 10.9, 10.1, 9.1, and 8.5 g/kg, P < 0.01, for TP SBM without supplemental phytase, TP SBM plus 500 phytase units of phytase/kg, LP SBM without supplemental phytase, and LP SBM plus phytase diets, respectively). Inclusion of phytase decreased tP and WSP excreted (P < 0.01), as did use of LP SBM (P < 0.01). Diet effects on the fraction of excreted tP that was WSP were observed (P < 0.01); however, there was not a significant effect of SBM source. Inclusion of exogenous phytase in diets increased the proportion of tP that was excreted as WSP from 55% in diets without phytase to 59% in diets containing phytase. The findings suggest that there is a need for LP soybeans as a dietary component to minimize environmental impacts.

Animal Feed↗

Bermudagrass management in the Southern Piedmont USA. V: Gastrointestinal parasite control in cattle.

Parasite-free pastures would improve cattle health and performance, resulting in possible economic return to producers. Our objective was to determine the effect of a single series of anthelmintic treatment of steers prior to stocking on Coastal bermudagrass pastures, during five consecutive summers, on the parasite burden in cattle. The site for this experiment had been conventionally cropped for several decades, with no exposure to cattle, and would be expected to be relatively free of nematode larvae. The experimental design was a randomized complete block (landscape features) with a split plot arrangement of treatments where main plots were pasture fertilization treatments (mineral, clover plus mineral, and broiler litter) and split plots were low and high forage mass. Anthelmintic treatment included pour-on ivermectin on day -21, albendazole on day -7, and injectable ivermectin 48 h prior to stocking of pastures, with the cattle remaining in drylot during the 48-h period prior to being placed on the experimental paddocks. All steers received only one series of treatments during any given year. Yearling Angus steers (Bos taurus) were managed in a put-and-take grazing system with three "tester" steers assigned to each paddock and "grazer" steers added or removed at 28-day intervals. From 1994 to 1998, steers grazed the paddocks for a 140-day period from mid May until early October each year. Fecal samples for worm egg counts were obtained on day 0 and at 28-day intervals, thereafter. On all sampling days after day 0, samples were obtained only from tester animals. Over the 5-year period, the mean eggs per gram of feces (epg) gradually increased from 0 (following treatment) to a mean of 2.2 (range from 0.7 to 3.0) by the end of the grazing season (the last sampling date) in October. Although the epg were not zero, they were below threshold levels that would allow development of a parasite burden in cattle. In traditional management systems, cattle graze parasite-contaminated pastures; therefore, parasites negatively impact growth and productivity throughout the entire grazing period. Periodic anthelmintic treatments simply give a temporary reprieve from those parasitic infections. Conceptually, using the current grazing system, it should be possible to maintain these pastures in a parasite-free status indefinitely; however, from a drug resistance perspective, it would be most applicable in sod-based rotation systems where cattle graze from two to five years before land is returned to row-crops. By removing the effect of parasites, cattle can grow without the physiological constraints that gastrointestinal parasites place on appetite, digestion, nutrient utilization, and general well being.

Albendazole↗

Jejunocolic anastomosis for the surgical management of recurrent cecal impaction in a horse.

A 5-year-old Thoroughbred gelding with recurrent cecal impaction refractory to medical management was treated with a side-to-side jejunocolic anastomosis. Cecal impaction did not recur after surgery. The horse gained weight and performed successfully for 14 months, but experienced three episodes of mild abdominal pain between 14 and 20 months after surgery. Mild cecal gas distention and firm ingesta in the colon were detected on rectal examination. The horse's feces remained soft after surgery, except during the colic episodes when dry, firm feces were passed.

Anastomosis, Surgical↗

Effect of plant species on the larvae of gastrointestinal nematodes which parasitise sheep.

Faeces containing Trichostrongylus colubriformis and/or Ostertagia circumcincta eggs were used to provide four contaminations in each of 2 years on plots of browntop, Yorkshire fog, ryegrass, tall fescue, lucerne, chicory, cocksfoot, white clover, and prairie grass and in the second year a mixed sward of ryegrass/white clover. Third stage larvae were recovered from faeces and from four strata of herbage, 0-2.5, 2.5-5, 5-7.5 and > 7.5 cm above the soil surface at 2, 4, 6, 8, 11, and 14 weeks after faeces were deposited on the swards. Herbage species had a significant (P < 0.0001) effect on the number of larvae recovered. Greatest numbers of larvae, as indicated by ranking analysis, were recovered from Yorkshire fog, ryegrass, and cocksfoot and lowest numbers from white clover and lucerne. The difference between herbages in numbers of larvae recovered was due to the "development success", the ability of larvae to develop to the infective stage and migrate on to herbage, rather than "survival", the rate of population decline once on the herbage. Faecal degradation was most rapid from white clover and browntop, intermediate from tall fescue, lucerne, prairie grass, cocksfoot, and ryegrass, and slowest from Yorkshire fog swards. The numbers of larvae recovered from herbages were related (r2 = 0.59, P < 0.05) with the faecal mass remaining. A greater proportion of the total larvae recovered from the herbage was recovered from the bottom stratum of Yorkshire fog and prairie grass than from white clover, with the other herbages intermediate, indicating that larvae had greater difficulty migrating up Yorkshire fog and prairie grass than the other herbage species. In most herbage species, despite more larvae being recovered from the lowest stratum, larval density (L3/kg herbage DM) was highest in the top stratum. This study has demonstrated that herbage species can have a significant impact on the population dynamics and vertical migration of T. colubriformis and O. circumcincta larvae.

Animals↗

Analysis of the intestinal microflora using molecular methods.

A large and complex bacterial community inhabits the distal intestinal tract of humans. This collection, known as the intestinal microflora, is dominated numerically by obligately anaerobic bacterial species. Many of these species have never been cultivated under laboratory conditions. Nucleic acid-based techniques now permit, however, the analysis of even the non-cultivable members of the bacterial community. Polymerase chain reaction (PCR) coupled with denaturing gradient gel electrophoresis (DGGE) provides a useful technique for comparisons of the composition of faecal or intestinal microfloras. PCR/DGGE has been shown to be useful in demonstrating changes that occur in the composition of the faecal microflora of infants administered antibacterial drugs. This research is important because treatment with oral antibiotics during the first 2 y of life has been identified as a predictor of subsequent atopic disease. The treatment of young children with broad spectrum oral antibiotics might produce perturbations in the composition of the intestinal microflora such that bacteria important in promoting Th1 mechanisms are depleted at a crucial age. This could result in Th2 dominance over Th1 immune responses to environmental antigens and an increased incidence of atopic disorders. PCR/DGGE provides a useful screening method to determine the impact of antibiotic treatment on the composition of the intestinal microflora of children and to identify the bacterial groups that are most affected.

Adult↗

A clinical trial of probiotic administration for prevention of Salmonella shedding in the postoperative period in horses with colic.

The purpose of this study was to evaluate the effects of probiotic administration on the prevalence of fecal shedding of Salmonella, the prevalence of postoperative diarrhea, the length of antimicrobial therapy, and the length of the hospitalization stay during the postoperative period in horses with colic. Two commercially available probiotics for horses were used in a double-blind prospective study of 200 horses undergoing surgery for colic. Probiotic or placebo was administered PO once a day for 7 days postoperatively, and fecal cultures for Salmonella were obtained daily for 10 days. After selection of 186 patients completing the treatment protocol, the results indicated that the commercial probiotic formulations had no effect on Salmonella shedding, prevalence of diarrhea, length of antimicrobial therapy, or length of hospitalization (P > .05). Twenty percent of the horses yielded 1 or more positive fecal cultures for Salmonella; of these horses, 74% were classified as asymptomatic shedders. Twenty-six percent of all horses had fluid diarrhea postoperatively, with only 12% of these horses having positive fecal cultures for Salmonella. The most common isolate was Salmonella krefeld (24 of 39 isolates). Among the different gastrointestinal disorders, horses with feed and sand impactions appeared to be more prone to shed Salmonella.

Animal Feed↗

Microbial impact of Canada geese (Branta canadensis) and whistling swans (Cygnus columbianus columbianus) on aquatic ecosystems.

Quantitative and qualitative analyses of the intestinal bacterial flora of Canada geese and whistling swans were carried out with the finding that wild birds harbor significantly more fecal coliforms than fecal streptococci. The reverse was typical of captive and fasting birds. Neither Salmonella spp. nor Shigella spp. were isolated from 44 migratory waterfowl that were wintering in the Chesapeake Bay region. Enteropathogenic Escherichia coli were detected in seven birds. Geese eliminated 10(7) and swans 10(9) fecal coliforms per day. Results of in situ studies showed that large flocks of waterfowl can cause elevated fecal coliform densities in the water column. From the data obtained in this study, it is possible to predict the microbial impact of migratory waterfowl upon aquatic roosting sites.

Animals↗

Effect of ivermectin (Mectizan) on intestinal nematodes.

Ancillary to a community based mass treatment campaign of onchocerciasis with ivermectin, assessment of the drug's effect on various intestinal nematodes was made in Bebeka, Southwest Ethiopia between 23 April and 23 July, 1990. A total of 231 people were invited for the study and all consented. From each, stool specimen was collected before treatment, two weeks and three months after administration of ivermectin at a dose of 150 mcg/kg body weight. Various intestinal parasites were observed in many of the samples, ranging from single parasite up to five mixed infections per slide. Efficacy of ivermectin against Strongyloides stercoralis was 100% throughout the observation period. Eggs of Ascaris lumbricoides were found in 74.5% of the stool samples collected before treatment and this was reduced to 3.5% and 48.9% in the post-treatment samples of 15 days and three months, respectively. Similar observation was made for the other geohelminths at a lower cure rate. This finding shows that apart from its primary purpose in the control of onchocerciasis, ivermectin has the added benefit of eliminating ascaris and strongyloides infection in areas where such parasites are co-endemic. Furthermore, its significant effect on the intensity of the other enteric nematodes will have a great impact on reducing transmission. The public health significance of population based mass chemotherapy with ivermectin is discussed.

Adolescent↗

Impact of infection by verotoxigenic Escherichia coli O157:H7 on the use of surgical services in a children's hospital.

OBJECTIVES: To determine the impact of Escherichia coli O157:H7 infection in children on the need for surgical assessment in a pediatric surgical practice and whether clinical and bacteriologic variables might contribute to that need. DESIGN: Examination of a case series. SETTING: A tertiary-care pediatric hospital. PATIENTS: Between 1990 and 1994, E. coli O157:H7 gastrointestinal infections were documented among 85 children, 29 of whom suffered from hemolytic-uremic syndrome. INTERVENTION: Surgical consultation for presumed or proven complications of the infection. MAIN OUTCOME MEASURES: The frequency of and reasons for surgical consultation, clinical and bacteriologic variables between patients who did or did not require surgical assessment. RESULTS: Of the 85 children, 17 (20%) were assessed by the surgical service. The majority of these children were inpatients. Two required abdominal surgery. Female gender, older age and progression to hemolytic-uremic syndrome were factors associated in univariate analyses with a likelihood of need for surgical assessment; variation in bacterial genotype was not. CONCLUSION: There is the potential for verotoxigenic E. coli O157:H7 infection to have a considerable impact on the utilization of pediatric surgical services.

Adolescent↗

Trophic transfer of cyanobacterial toxins from zooplankton to planktivores: consequences for pike larvae and mysid shrimps.

The aim of this study was to evaluate the potentially harmful effects of zooplankton preexposed to cyanobacteria on two planktivorous animals: a fish larva (pike, Esox lucius) and a mysid shrimp (Neomysis integer). The planktivores were fed zooplankton from a natural community that had been preexposed to cell-free extract or to purified toxin (nodularin) of the cyanobacterium Nodularia spumigena, and the growth, feeding, and pellet production of the planktivores, as well as the toxin content of the pellets, were measured. In addition, radiolabeled nodularin ((3)H-dihydronodularin) was used in separate experiments to measure the vector transfer of nodularin from zooplankton to their predators. During 11-day exposures, dissolved nodularin was transferred to pike larvae and N. integer via zooplankton at very low rates of accumulation. Treatment with N. spumigena extract decreased the ingestion and feces production rates of pike larvae. With purified nodularin alone, no such effect could be observed. No effect on molting cycle length, fecal pellet production, C:N ratio, or growth of N. integer was detected. The results suggest that dissolved cyanobacterial toxins released during bloom decay can have a negative impact on feeding and, hence, on the growth of fish larvae via zooplankton, even without direct contact between cyanobacteria and the fish.

Animals↗