Sensitization to Gibberellin-Regulated Protein (Peamaclein) Among Italian Cypress Pollen-Sensitized Patients.

BACKGROUND AND OBJECTIVES: Peach gibberellin-regulated protein (peamaclein) has recently emerged as a relevant food allergen in cypress pollen-hypersensitive patients. Objective: We investigated monosensitization to peamaclein among Italian cypress pollen-allergic patients. MATERIAL AND METHODS: A total of 835 cypress pollen-hypersensitive patients from 28 Italian allergy centers underwent a thorough work-up to determine food-allergic reactions and performed skin prick testing with a commercial peach extract containing peamaclein. IgE to rPru p 3 was measured in peach reactors, and those with negative results were enrolled as potentially monosensitized to peamaclein. IgE reactivity to rPru p 7 was evaluated using immunoblot and an experimental ImmunoCAP with rPru p 7. RESULTS: Skin prick tests were positive to peach in 163 patients (19.5%); however, 127 (77.9%) were excluded because they reacted to Pru p 3. Twenty-four patients (14.7%) corresponding to 2.8% of the entire study population) were considered potentially monosensitized to peamaclein. No geographic preference was observed. Seventeen of the 24 patients (70.8%) had a history of food allergy, mainly to peach (n=15). Additional offending foods included other Rosaceae, citrus fruits, fig, melon, tree nuts, and kiwi. On peach immunoblot, only 3 of 18 putative peamaclein-allergic patients reacted to a band at about 7 kDa; an additional 4 patients reacted at about 50-60 kDa. Ten of 18 patients (56%) had a positive result for Pru p 7 on ImmunoCAP. CONCLUSION: Allergy and sensitization to peamaclein seem rare in Italy. Most patients react to peach, although other Rosaceae fruits and several citrus fruits may also be offending foods. Peach and cypress pollen probably also share cross-reacting allergens other than peamaclein.

Role for neonatal D-serine signaling: prevention of physiological and behavioral deficits in adult Pick1 knockout mice.

NMDA glutamate receptors have key roles in brain development, function and dysfunction. Regulatory roles of D-serine in NMDA receptor-mediated synaptic plasticity have been reported. Nonetheless, it is unclear whether and how neonatal deficits in NMDA-receptor-mediated neurotransmission affect adult brain functions and behavior. Likewise, the role of D-serine during development remains elusive. Here we report behavioral and electrophysiological deficits associated with the frontal cortex in Pick1 knockout mice, which show D-serine deficits in a neonatal- and forebrain-specific manner. The pathological manifestations observed in adult Pick1 mice are rescued by transient neonatal supplementation of D-serine, but not by a similar treatment in adulthood. These results indicate a role for D-serine in neurodevelopment and provide novel insights on how we interpret data of psychiatric genetics, indicating the involvement of genes associated with D-serine synthesis and degradation, as well as how we consider animal models with neonatal application of NMDA receptor antagonists.

The importance of educating subjects entitled to use an adrenaline auto-injector for self-administration.

An educational program, consisting in a clear explanation of the technical aspects and use of the adrenaline auto-injection devices (AAD) and in a practical test utilizing a demonstration kit was given to 350 patients from our outpatient clinic. AAD was also distributed to 50 patients formerly followed by another allergy clinic without training. At practical control test, only 10% of the untrained patients where able to correctly use the AAD versus 80% of trained subjects. Since AAD is a life-saving procedure in severe anaphylactic episodes, this attempt to improve the ability of the patient to comply with the procedure can improve the efficacy of the treatment and eventually the patient's health.

Prevalence and incidence of reactions to insect stings in children: a reappraisal.

AIM: The prevalence of systemic reactions (SR) to Hymenoptera stings in children was estimated in values lower than 1% in early studies but much higher in recent surveys. We evaluated the current prevalence and the incidence of SR and large local reactions (LLR) to Hymenoptera stings in children in Italy. METHODS: The data on children were collected from the database of the population study on the city of Cotignola, analyzing the answers to the part of the questionnaire about Hymenoptera stings, that concerned if the subject was ever stung by apids or vespids, if there has been a SR or a LLR, and if subjects with reactions received a diagnostic evaluation and a medical treatment. RESULTS: Of the population of 1035 children, 173 (16.7%) were stung at least one time by Hymenoptera. Of them, 5 had had a SR and 9 had had a LLR. This defines a prevalence of SR of 0.5% and of LLR of 0.9%. Only one reaction was severe. Of the 14 subjects with SR or LLR, 5 (35.7%) underwent a diagnostic evaluation and one (7.1%) was treated with venom immunotherapy. The incidence of SR in the subsequent 2 years was 0.09% in the first year and 0.08% in the second year. CONCLUSIONS: These findings do not confirm the recent reports of an increased prevalence of Hymenoptera venom allergy in children. The incidence of SR to stings, thus far unreported for children, was very low both in the first and in the second year.

Fever of unknown origin as unique symptom of an indolent mastocytosis.

A 39-years-old man afferred to our hospital for a fever lasting for more than 6 months, without abnormalities at physical examination (in particular no skin alterations); a recent laboratory and instrumental investigation was ineffective and so a fever of unknown origin (FUO) was diagnosed Since he reported an history of infantile mastocytosis (usually auto-resolving) we evaluated his serum-tryptase levels that resulted of 49 ug/L (normal value 20 ug/L), raising the doubt of the presence of an active mastocytosis. The following bone marrow evaluation showed aggregates of CD117 positive cells and a c-Kit point mutation at codon D 816V confirming the diagnosis of indolent mastocytosis.The present case confirm that FUO can be caused by an otherwise asymptomatic indolent mastocytosis, thus suggesting to include the serum-tryptase level measurement in the diagnostic approach to this pathological condition, at least in selected cases.

Allergy to beer in LTP-sensitized patients: beers are not all the same.

BACKGROUND: Most cases of beer allergy reported so far have been associated with hypersensitivity to the non-specific lipid transfer protein (LTP). In view of the marked differences in brewing processes we assessed IgE reactivity as well as tolerance to many different beers in an allergic patient. METHODS: A 45 year-old man hypersensitive to grass pollen, cat dander and Alternaria tenuis with a history of urticaria and dyspnoea after drinking beer and a weak skin reactivity to commercial corn extract was studied. The patient underwent SPT with 36 different brands of beer and an open challenge with those scoring negative was performed. An immunoblot analysis was carried out using 2 SPT-positive beers, 2 SPT-negative beers, and barley, wheat, and maize extracts using both patient's serum and a maize LTP-specific in-house developed polyclonal antibody from rabbit. Further, the immune reactive LTP of one beer was separated by HPLC and the chromatogram was compared to that of purified maize LTP. RESULTS: Beer SPT scored positive in 30/36 cases. The immunoblot analysis showed IgE reactivity at about 10 kDa against the two SPT-positive beers and against maize with both patient's serum and the polyclonal anti-LTP rabbit serum, whereas the two SPT-negative beers, and barley extract scored negative. The immunodetected protein co-migrated with maize LTP. CONCLUSION: In beer-allergic patients the diagnostic workup may point to the detection of some tolerated products that can be consumed risk-free.

Prevalence of allergic disorders in Italy: the Cotignola population study.

BACKGROUND: The worldwide prevalence of allergic diseases such as rhinitis, asthma, and atopic dermatitis is continuously increasing, while other allergic disorders such as urticaria and angioedema are less investigated. We performed a population study evaluating the prevalence of any kind of allergic disorders. METHODS: The entire population of 7,201 inhabitants of Cotignola (Ravenna, Italy) was surveyed by a questionnaire assessing symptoms related to rhinitis, asthma, anaphylaxis, skin symptoms and insect sting allergy as well as the features of clinical presentations, diagnosis, and treatment received. RESULTS: Valid questionnaires were obtained by 6,676 inhabitants (92.7%). The sample was formed by 3,266 males and 3,495 females, the mean age was 45.6 years; 1,035 subjects (15.5%) were aged less than 18 years; 404 subjects (6%) had at least one episode of wheezing/breathlessness in their lifetime, and 243 of them (60.1%) had a diagnosis of asthma; 1,002 subjects (14.8%) had nose symptoms in their lifetime, and 375 of them (37.4%) had a diagnosis of allergic rhinitis or rhinoconjunctivitis. For other allergic manifestations, data were obtained from 5,730 subjects; of them, 178 (3.1%) had skin symptoms, 59 (1.1%) had oral symptoms, and 37 (0.6%) had anaphylaxis; 207 (3.6%) had reactions to insect stings. There were no significant differences in prevalence between Italians and immigrants. Only 51.7% of subjects with asthma, 46.5% of those with rhinitis, 22.7% of those with other allergies, but 97.1% of those with insect allergy, received treatment. CONCLUSIONS: These findings confirm recent data on epidemiology of allergic diseases in Europe, particularly in Italy, and add some details on how such diseases are managed.

Shrimp allergy in Italian adults: a multicenter study showing a high prevalence of sensitivity to novel high molecular weight allergens.

BACKGROUND: Shrimp is a frequent cause of food allergy worldwide. Besides tropomyosin, several allergens have been described recently. OBJECTIVE: We investigated which allergens are involved in Italian shrimp-allergic adults. METHODS: Sera from 116 shrimp-allergic patients selected in 14 Italian allergy centers were studied. Skin prick tests with house dust mite (HDM) as well as measurements of IgE to Pen a 1 (shrimp tropomyosin) and whole shrimp extract were performed. All sera underwent shrimp immunoblot analysis, and inhibition experiments using HDM extract as inhibitor were carried out on some Pen a 1-negative sera. RESULTS: Immunoblots showed much variability. IgE reactivity at about 30 kDa (tropomyosin) was found in <50% of cases, and reactivity at about 67 kDa and >90 kDa was frequent. Further reactivities at 14-18, 25, 43-50, about 60 and about 80 kDa were detected. Most subjects had a history of shrimp-induced systemic symptoms irrespective of the relevant allergen protein. IgE to Pen a 1 were detected in sera from 46 (41%) patients. Skin reactivity to HDM was found in 43/61 (70%) Pen 1-negative subjects and inhibition studies showed that pre-adsorption of sera with HDM extract induced a marked weakening of the signal at >67 kDa. CONCLUSIONS: Several allergens other than tropomyosin are involved in shrimp allergy in adult Italian patients. Some hitherto not described high molecular weight allergens seem particularly relevant in this population and their cross-reactivity with HDM allergens makes them novel potential panallergens of invertebrates.

Are IgE levels to foods other than rosaceae predictive of allergy in lipid transfer protein-hypersensitive patients?

BACKGROUND: Lipid transfer protein (LTP), the most frequent cause of primary food allergy in Italy, is a cross-reacting plant pan-allergen. Markers able to predict whether a patient sensitized to a certain food but not yet clinically allergic will develop allergy would be extremely helpful. OBJECTIVE: It was the aim of this study to investigate the relevance of IgE levels to some plant foods other than Rosaceae as predictors of either local or systemic allergic reaction in LTP-allergic subjects. METHODS: One hundred (40 males, 60 females , mean age 29 years) peach-allergic patients monosensitized to LTP seen at 14 Italian centres in 2009 were studied. Walnut, hazelnut, peanut, tomato, rice and/or maize allergy was ascertained by interview and confirmed by positive skin prick test. IgE levels to these foods and to rPru p 3 were measured. RESULTS: Higher levels of IgE to Pru p 3 were associated with a higher prevalence of allergy to hazelnut, peanut and walnut. For all study foods, except rice, median IgE levels in allergic subjects significantly exceeded those in tolerant subjects, though within single allergic groups, the differences between patients reporting systemic or local (oral) symptoms were not significant. Ninety-five percent cut-off IgE levels predictive of clinical allergy were established for study foods although the marked overlaps between allergic and tolerant subjects made them of limited usefulness. CONCLUSION: Specific IgE levels are only partially predictive of clinical allergy. The reasons why some individuals showing low specific IgE levels develop clinical allergy whereas others showing high IgE levels do not, despite similar exposure to the allergen, remain unclear.

A case of anaphylaxis: horse-fly or hymenoptera sting?

In literature it has been described a high risk of systemic reaction after blood-sucking Dyptera bites, like mosquitoes and horsefly, in people sensitive to hymenoptera. A 51 year old man, allergic to hymenoptera venom and with a history of i.v. reaction after Mueller, who has been treated with Vespula sp. ITS for the last 3 years, was stung by a yellow, black and green insect on the neck. Five minutes after the bite, he suffered generalized hitching and urticaria, oral cavity and lower limbs paresthesia, followed by lost of consciousness. At the Emergency Room he was successfully treated with adrenaline, intravenous antihistamines and corticosteroid. The description of the insect as well as the lack of the sting on the site suggested a wasp as the culprit. By studying one of these insect that has been captured by the patient, it turned out it wasn't a Vespula, but a horsefly, the Tabanus bovinus, which resembles Hymenoptera. Skin prick test and RAST for Tabanus confirmed the allergology diagnosis. In conclusion, also Tabanus bovines can cause systemic reaction up to anaphylactic shock.

CD30 serum levels and response to hymenoptera venom immunotherapy.

BACKGROUND: The glycoprotein CD30 is expressed and released by T lymphocytes that secrete type 2 helper cytokines of (T(H)2). These molecules play a role in the pathogenesis of allergic diseases. Venom immunotherapy has proven to be very effective in hymenoptera venom allergy through a shift in cytokine production from T(H)2-type cytokines to T(H)1-type cytokines. OBJECTIVE: To evaluate the relationship between the soluble form of CD30 (sCD30) and venom immunotherapy in patients with hymenoptera venom allergy. MATERIALS AND METHODS: sCD30 levels were assayed by enzyme-linked immunosorbent assay in the sera of 61 healthy controls and 14 patients with hymenoptera venom allergy who had undergone immunotherapy before treatment and 1,3, and 12 months after treatment started. Nine patients were allergic to Apis venom, 4 to Vespula venom, and 1 to Polistes venom. RESULTS: CD30 serum levels (median, interquartile range) were significantly higher in venom-allergic patients before treatment (33.6 U/mL; 14.8-61.6) than in controls (9.7 U/mL, 1.9-21.3) (P < .000). These levels decreased progressively during treatment in all patients except 2 (P < .000). At the third month of therapy, the levels reached statistical significance in comparison with baseline. CONCLUSIONS: This study shows that sCD30 levels are significantly higher in patients with hymenoptera venom allergy and indirectly confirms a preferential T(H)2-type cytokine production in these patients. sCD30 expression decreases during immunotherapy, thus confirming the immunomodulatory role of this treatment in promoting a shift to T(H)1-type cytokines.

The wasp-horsefly syndrome.

Here are two cases of two male patients of 57 and 62 years of age, already known as allergic to stinging hymenoptera venom, who after a horsefly bite have presented a serious 3-4 degree-type Mueller classification systemic reaction. The diagnosis has been carried out clinically and after an accurate environmental anamnesis and along with prick tests and RAST, further specific entomological confirm. In literature the so called wasp-mosquito-syndrome has been indicated where hyaluronidase has been referred to as the cross allergen, between the hymenoptera venom and the mosquito saliva, which likely triggers the reaction. We believe that it is also possible to take into consideration a wasp-horsefly-syndrome as well, supposing the increased risk of anaphylactic reactions to Tabanidae bites, relatively frequent in areas with animals and streams, in subjects sensitized to stinging hymenoptera. We also suggest the possibility that in these subjects some systemic reactions are due in fact to Tabanidae bites and not so much for the failure of a possible active ITS of stinging hymenoptera.

Safety of etoricoxib in patients with reactions to NSAIDs.

BACKGROUND: Adverse reactions to nonsteroidal anti-inflammatory drugs (NSAIDs) are a frequently reported problem due to the fact that these molecules are often used for control of pain and inflammation. Although the use of selective inhibitors of cyclooxygenase (COX) 2 helps to prevent some of these adverse reactions, they can have cardiac side effects when taken for prolonged periods. Here we report the safety and tolerability of etoricoxib, a selective COX-2 inhibitor with fewer cardiovascular effects, in patients with adverse reactions to NSAIDs. PATIENTS AND METHODS: We performed placebo-controlled oral challenge with etoricoxib in 65 patients with previous adverse reactions to NSAIDs: 13 to salicylates, 18 to arylpropionic acids, 10 to arylacetic acid, 12 to oxicam and derivates, 8 to pyrazolones, and 4 to acetaminophen (paracetamol). The reported symptoms were urticaria or angioedema in 69%, rhinitis in 3%, and 1 case of anaphylactic shock (1.5%). The challenge was done using the placebo on the first day, half dosage of etoricoxib (45 mg) on the second day, and the therapeutic dose of 90 mg on the third day. The challenge was done in the outpatient department of the hospital and the subjects were monitored for a further 4 to 6 hours after challenge. RESULTS: Oral challenge with etoricoxib was well tolerated in 97% of the patients. Only 2 systemic reactions were reported during the challenge test. CONCLUSION: Etoricoxib can be considered a safe molecule for those patients with previous adverse reactions to NSAIDs.

Ventricular fibrillation after a hymenoptera sting.

A 54-year-old male, who had presented 2 ventricular fibrillation (VF) episodes with post-anoxic coma and later a return to consciousness and to a sinusal rhythm after defibrillation, have been placed a ventricular intracavitary stimulator (AICD). Since all the tests including the coronarygraphy have been found normal, we have paid attention to the anamnesis revealing an Apis mellifera sting before both VF episodes, previously considered irrelevant for the absence of relevant local symptoms. Intracutaneous tests were negative to Vespula sp. and positive to A. mellifera extract at a concentration of 0.01 mug/ml. Specific IgE for A. mellifera venom presented values of 2,36 U/ml for A. mellifera and <0.35 U/ml per Vespula sp. and Polistes dominulus. The patient was then submitted to ITS with A. mellifera aqueous extract. During the RASH treatment no adverse reactions have been observed, whereas we witnessed a major adverse reaction, 3 min after the first 100 mcg maintenance dose, controlled with anti-H1 and cortisone reaction, nevertheless no reactions were observed during the 3 years the same dosage has been repeated monthly. Our case supports the hypothesis of an anaphylactic reaction as trigger of vasoconstriction in individuals affected by ventricular arrhythmia not explained with other causes such as a coronary disease, a myocardiopathy or a pharmacological toxicity. Arrhythmia can be a serious outbreak of a mediated IgE allergic reaction even without any relevant local symptoms. The diagnostics with lyophilized A. mellifera venom has been proven safe in a patient who suffered a cardiac anaphylaxis.

Focal nodular hyperplasia after busulfan treatment.

The case of a 48-year-old woman in whom focal nodular hyperplasia of the liver developed after busulfan therapy was administered for essential thrombocytosis is described. Focal nodular hyperplasia is a reactive disorder related to a circulation disorder. The close temporal relation between the haematological disease, busulfan treatment and the appearance of hyperplastic diseases of the liver in our patient supports the possibility that the association of the events might not be casual.

Anaphylactic shock to Argas reflexus bite.

Anaphylaxis is a severe, life-threatening allergic reaction, affecting both children and adults. The occurrence of anaphylaxis is not as rare as generally believed (1.21% to 15.04% of the US population). Often the cause of this reaction remain unknown, mainly due to the difficulty in defining the outbreaking causes. Herein, we describe an interesting case of a patient, who developed an anaphylactic reaction after the bite of a pigeon tick. During the last 2 years, in wintertime, the patient often came to the emergency room for general rash and swelling, hypotension and tachycardia preceded by itching and general distress. Notably, the symptoms manifested themselves as night fell. In two particular occasions the patient reached the hospital in a state of shock. After another episode of general swelling, the patient was invited to examine her domestic environment. She brought us some parasites, collected at home, particularly on the bed. A morphological examination by entomologists proved these parasites to belong to Argas reflexus (Arg.r.), one of the 31 species of soft ticks. The presence of specific IgE to a protein secreted by the Arg.r. salivary glands was in favour of immediate-type systemic reaction, as supposed by the clinical history.

Effects of hydroclimatic anomalies on bacteriological quality of the Middle Paraná River (Santa Fe, Argentina) / Efecto de anomalías hidroclimáticas sobre la calidad bacteriológica del río Paraná Medio (Santa Fe, Argentina)

Lenitic and lotic aquatic environments were studied in the Middle Paraná River basin, one of the largest rivers of the world (basin: 1,510,000 km2, length: 2,570 km). The Paraná River (S 31° 42’ 04"; W 60° 29’ 39"), during El Niño-Southern Oscillation (ENSO) (1997-1998), registered maximum flows of 29,962 m3 s-1(more than twice the mean flow) and also positive pluvial anomalies (A) (from +120 mm to +161 mm). However, concentrations of Escherichia coli remained low, with values similar to the mean (p > 0.05) (1.3802 log10 cfu/100 ml). Only a maximum peak (1.903 log10 cfu/100 ml), significantly higher than the mean (p < 0.0001), was detected during the ascending phase of the flood pulse. During La Niña (September 1999 - March 2000; Q =11,255 m3 s-1; A = -78 mm to -84 mm), concentrations of E. coli were significantly lower than the mean (p< 0.0001). During the post-Niña period, with normal flows (Q = 14,900 m3 s-1) but with strong positive pluvial anomalies (A= +118 mm to +377 mm), the fecal indicator density reached maximum values (up to 2.699 log10 cfu /100 ml, p< 0.0001). The multiple regression model used with all the results obtained in the Paraná River showed that variations in concentrations of E. coli are mainly explained by pluvial precipitations and hydrometric level (p = 0.001). Temporal patterns of concentrations of E. coli in a small, secondary course (Q = 101 m3 s-1) followed those of the Paraná River, but concentrations and peaks of E. coli produced by exceptional rains showed a higher magnitude (maximum: 3.325 log10 cfu /100 ml). In the floodplain lakes, away from urban centers, concentrations of E. coli were not associated to hydroclimatic anomalies, but directly to vegetable cover: maximum concentrations were always registered during periods that lakes remained covered by floating macrophytes (mainly Eichhornia crassipes); on the contrary, minimum concentrations were registered during periods without vegetable cover.

Se estudiaron ambientes acuáticos leníticos y lóticos en la cuenca del río Paraná Medio, uno de los ríos más grandes del mundo (cuenca: 1.510.000 km2, longitud: 2.570 km). El río Paraná (31° 42’ 04"S; 60° 29’39"W), durante El Niño Oscilación Sur (ENOS) (1997-1998), registró caudales máximos de 29.962 m3 s-1(más del doble del caudal medio) y también anomalías pluviales (A) positivas (desde +120mm a +161mm). Sin embargo, la concentración de Escherichia coli se mantuvo baja, con valores similares (p > 0,05) a la media (1,3802 log10ufc/100ml). Solamente se detectó un pico máximo (1,903 log10ufc/100ml) significativamente mayor a la media (p < 0,0001) durante la fase ascendente del pulso de la creciente. Durante La Niña (sept. 1999 - marzo 2000; Q =11.255 m3 s-1 ;A = -78mm a -84mm), las concentraciones de E. coli resultaron inferiores a la media (p<0,0001). Durante el período post-Niña, con caudales normales (Q = 14.900 m3 s-1) pero con fuertes anomalías pluviales positivas (A= +118 mm a +377mm), la densidad del indicador fecal alcanzó valores máximos (hasta 2,699 log10ufc /100ml, p< 0,0001).La aplicación de un modelo de regresión múltiple al conjunto de los resultados obtenidos en el río Paraná, muestra que las variaciones en la concentración de E. coli son principalmente explicadas por las precipitaciones pluviales y el nivel hidrométrico (p = 0,001). Los patrones temporales de las concentraciones de E. coli en un pequeño cauce secundario (Q = 101 m3s-1) siguieron a las del río Paraná, pero las concentraciones y los picos de E. coli producidos por lluvias excepcionales fueron de mayor magnitud (máximo: 3,325 log10ufc /100ml). Enlas lagunas de la llanura de inundación, lejos de centros urbanos, la concentración de E. coli no estuvo asociada con anomalías hidroclimáticas, sino directamente con la cobertura vegetal: las concentraciones máximas se registraron siempre durante los períodos que permanecían cubiertas con macrófitas flotantes (principalmente Eichhornia crassipes). Durante los períodos sin cobertura vegetal, por el contrario, se registraron las concentraciones mínimas de E. coli.

Effects of hydroclimatic anomalies on bacteriological quality of the Middle Paraná River (Santa Fe, Argentina).

Lenitic and lotic aquatic environments were studied in the Middle Paraná River basin, one of the largest rivers of the world (basin: 1,510,000 km2, length: 2,570 km). The Paraná River (S 31 degrees 42' 04"; W 60 degrees 29' 39"), during El Niño-Southern Oscillation (ENSO) (1997-1998), registered maximum flows of 29,962 m3 s(-1) (more than twice the mean flow) and also positive pluvial anomalies (A) (from +120 mm to +161 mm). However, concentrations of Escherichia coli remained low, with values similar to the mean (p > 0.05) (1.3802 log10cfu/100 ml). Only a maximum peak (1.903 log10cfu/100 ml), significantly higher than the mean (p < 0.0001), was detected during the ascending phase of the flood pulse. During La Niña (September 1999-March 2000; Q = 11,255 m3 s(-1); A = -78 mm to -84 mm), concentrations of E. coli were significantly lower than the mean (p < 0.0001). During the post-Niña period, with normal flows (Q = 14,900 m3 s(-1)) but with strong positive pluvial anomalies (A = +118 mm to +377 mm), the fecal indicator density reached maximum values (up to 2.699 log10cfu/100 ml, p < 0.0001). The multiple regression model used with all the results obtained in the Paraná River showed that variations in concentrations of E. coli are mainly explained by pluvial precipitations and hydrometric level (p = 0.001). Temporal patterns of concentrations of E. coli in a small, secondary course (Q = 101 m3 s(-1)) followed those of the Paraná River, but concentrations and peaks of E. coli produced by exceptional rains showed a higher magnitude (maximum: 3.325 log10cfu/100 ml). In the floodplain lakes, away from urban centers, concentrations of E. coli were not associated to hydroclimatic anomalies, but directly to vegetable cover: maximum concentrations were always registered during periods that lakes remained covered by floating macrophytes (mainly Eichhornia crassipes); on the contrary, minimum concentrations were registered during periods without vegetable cover.