Lesión medular asociada a hematoma epidural espinal espontáneo / Spinal cord injury associated with spontaneous spinal epidural hematoma

Introducción: El hematoma epidural espinal espontáneo (HEEE) es una entidad de baja incidencia, de elevada morbimortalidad y que causa una importante limitación funcional en la vida de los pacientes. Material y métodos: Con el objetivo de determinar la incidencia del HEEE y el tipo de lesión medular provocada y su repercusión funcional en este centro hospitalario, se realizó un estudio descriptivo retrospectivo analizando variables demográficas, de la lesión (ISCNSCI) y de la funcionalidad (SCIMIII). Resultados: Se revisaron los casos de HEEE atendidos en este centro. El 75% eran varones, con una mediana de edad de 55años. Todas las lesiones fueron incompletas. La localización más frecuente de las lesiones fue a nivel cervical bajo y dorsal alto. La mitad de los sangrados se produjeron en la región medular anterior. Se objetivó mejoría funcional tras el programa específico de rehabilitación. Conclusión: El HEEE podría considerarse de buen pronóstico funcional, relacionado con lesiones medulares habitualmente posteriores e incompletas sensitivo-motoras que se beneficiarían de un tratamiento rehabilitador específico precoz.(AU)

Introduction: Spontaneous spinal epidural hematoma (SSEH) is a disease with low incidence and high morbidity/mortality. It can cause severe loss of function. Material and methods: In order to determine the incidence, type of spinal injury and functional impact, a descriptive and retrospective study was developed, analysing demographic data, functional scores (SCIMIII) and neurological scores (ISCNSCI). Results: Cases of SSEH were reviewed. Seventy-five percent were male, median age was 55years old. All of the spinal injuries were incomplete and were frequently in the lower cervical and thoracic regions. Fifty percent of bleedings occurred in the anterior spinal cord. Most showed with a progress after an intensive rehabilitation program. Conclusion: SSEH could be considered to have a good functional prognosis, related to usually posterior and incomplete sensory-motor spinal cord injuries that would benefit from early specific rehabilitative treatment.(AU)

New perspectives on morphological and genetic variability of Corynosoma bullosum [Linstow, 1892] parasitizing southern elephant seals from the Antarctic Peninsula.

Previous descriptions of Corynosoma bullosum (Linstow, 1892) show that specimens vary greatly in the proportions of different body structures, measurements of females and males, number of rows of hooks, and egg measurements, among other features. We redescribe this species from specimens found in southern elephant seal faeces from King George Island. We also provide a molecular characterization, in addition to 5.8S and internal transcribed spacer (ITS) existing sequences. We examined 41 elephant seals, and 30 adult acanthocephalans were found in 15 of them. The specimens were identified as belonging to the genus Corynosoma due to each having a tubular body with an inflated anterior part forming a thorny disk and the posterior part bearing somatic spines on the ventral surface, and genital spines surrounding the genital pore. Individual morphology corresponded to C. bullosum: large size, marked sexual dimorphism, and proboscis with 16-18 rows of spines with 11-15 spines per row. The molecular profile of three specimens of C. bullosum was analysed using 18S rDNA. We inferred phylogenetic relationships of the family Polymorphidae using maximum likelihood and Bayesian inference. We provide an updated morphological redescription for C. bullosum including electron microscopy photographs and molecular data. The 18S gene sequences showed low genetic variation and supported that C. bullosum is a sister to Corynosoma australe.

[Spinal cord injury associated with spontaneous spinal epidural hematoma]. / Lesión medular asociada a hematoma epidural espinal espontáneo.

INTRODUCTION: Spontaneous spinal epidural hematoma (SSEH) is a disease with low incidence and high morbidity/mortality. It can cause severe loss of function. MATERIAL AND METHODS: In order to determine the incidence, type of spinal injury and functional impact, a descriptive and retrospective study was developed, analysing demographic data, functional scores (SCIMIII) and neurological scores (ISCNSCI). RESULTS: Cases of SSEH were reviewed. Seventy-five percent were male, median age was 55years old. All of the spinal injuries were incomplete and were frequently in the lower cervical and thoracic regions. Fifty percent of bleedings occurred in the anterior spinal cord. Most showed with a progress after an intensive rehabilitation program. CONCLUSION: SSEH could be considered to have a good functional prognosis, related to usually posterior and incomplete sensory-motor spinal cord injuries that would benefit from early specific rehabilitative treatment.

Os subtibiale: esa rara molestia en el tobillo / Os subtibiale: That odd ankle pain

El os subtibiale es un hueso accesorio del tobillo, poco frecuente. Localizado en el colículo posterior del maléolo tibial interno, puede verse en edad pediátrica y adulta. Puede causar dolor, enrojecimiento y/o inflamación del tobillo, pudiendo llevar al diagnóstico erróneo de fractura avulsiva. Su conocimiento anatómico es crucial. Se presenta el caso de un paciente en edad escolar, valorado en consulta por dolor en la cara interna de ambos tobillos durante 2 meses tras traumatismo casual. En segundo lugar, un paciente adulto con dolor en la cara interna del tobillo derecho de 3 días de evolución, sin traumatismo, valorado en urgencias. Es imprescindible la correcta anamnesis y exploración física. El diagnóstico se realiza mediante radiología convencional de tobillos, proyección anteroposterior y lateral en carga. El tratamiento inicial es conservador (férulas u ortesis) para establecer y mantener las funciones del pie durante las actividades en carga. Si persiste tras 6 meses, se podría plantear tratamiento quirúrgico (AU)

Os subtibiale is a low prevalence accessory bone of the ankle. This bone is located in the posterior colliculus of the tibial medial malleolus, both in paediatric and adult ages. It can cause pain, redness and/or swelling, which can lead to a mistaken diagnosis of avulsion fracture. Adequate anatomical knowledge is crucial. First, we present the case of a school-aged boy, seen at the outpatient clinic for a 2-month history of pain in both inner ankles after an injury. Second, we present the case of an adult patient with a 3-day history of right medial ankle pain, with no previous injury, evaluated at the Emergency Department. Accurate history-taking and physical examination are essential. The diagnosis is given by conventional radiology of both ankles, in antero-posterior and lateral load views. The initial treatment is conservative (splint or orthesis) to establish and maintain the function of the foot during loading activities. If there is no recovery after 6 months, surgical treatment can be considered (AU)

[Os subtibiale: That odd ankle pain]. / Os subtibiale: esa rara molestia en el tobillo.

Os subtibiale is a low prevalence accessory bone of the ankle. This bone is located in the posterior colliculus of the tibial medial malleolus, both in paediatric and adult ages. It can cause pain, redness and/or swelling, which can lead to a mistaken diagnosis of avulsion fracture. Adequate anatomical knowledge is crucial. First, we present the case of a school-aged boy, seen at the outpatient clinic for a 2-month history of pain in both inner ankles after an injury. Second, we present the case of an adult patient with a 3-day history of right medial ankle pain, with no previous injury, evaluated at the Emergency Department. Accurate history-taking and physical examination are essential. The diagnosis is given by conventional radiology of both ankles, in antero-posterior and lateral load views. The initial treatment is conservative (splint or orthesis) to establish and maintain the function of the foot during loading activities. If there is no recovery after 6 months, surgical treatment can be considered.

Widespread infection of Areospora rohanae in southern king crab (Lithodes santolla) populations across south Chilean Patagonia.

Cottage cheese disease is caused by microsporidian parasites that infect a wide range of animal populations. Despite its potential to affect economically important activities, the spatial patterns of prevalence of this disease are still not well understood. Here, we analyse the occurrence of the microsporidian Areospora rohanae in populations of the king crab Lithodes santolla over ca 800 km of the southeastern Pacific shore. In winter 2011, conical pots were deployed between 50 and 200 m depth to capture crabs of a wide range of sizes. The infection was widely distributed along the region, with a mean prevalence of 16%, and no significant association between prevalence and geographical location was detected. Males, females and ovigerous females showed similar prevalence values of 16.5 (13-18.9), 15 (9.2-15) and 16.7% (10-19%), respectively. These patterns of prevalence were consistent across crab body sizes, despite the ontogenetic and sex-dependent variations in feeding behaviour and bathymetric migrations previously reported for king crabs. This study provided the first report of the geographical distribution of A. rohanae infecting southern king crabs.

The phylogeny and life cycle of two species of Profilicollis (Acanthocephala: Polymorphidae) in marine hosts off the Pacific coast of Chile.

Resolving complex life cycles of parasites is a major goal of parasitological research. The aim of this study was to analyse the life cycle of two species of the genus Profilicollis, the taxonomy of which is still unstable and life cycles unclear. We extracted individuals of Profilicollis from two species of crustaceans (intermediate hosts) and four species of seagulls (definitive hosts) from sandy-shore and estuarine habitats along the south-east Pacific coast of Chile. Mitochondrial DNA analyses showed that two species of Profilicollis infected intermediate hosts from segregated habitats: while P. altmani larvae infected exclusively molecrabs of the genus Emerita from fully marine habitats, P. antarcticus larvae infected the crab Hemigrapsus crenulatus from estuarine habitats. Moreover, P. altmani completed its life cycle in four seagulls, Chroicocephalus maculipennis, Leucopheus pipixcan, Larus modestus and L. dominicanus, while P. antarcticus, on the other hand, completed its life cycle in the kelp gull L. dominicanus. Accordingly, our results show that two congeneric parasites use different and spatially segregated species as intermediate hosts, and both are capable of infecting one species of definitive hosts. As such, our analyses allow us to shed light on a complex interaction network.

Pan-American marine coastal distribution of the acanthocephalan Profilicollis altmani based on morphometric and phylogenetic analyses of cystacanths from the mole crab Emerita brasiliensis.

Thorny-headed acanthocephalan worms of the genus Profilicollis are widely distributed in the oceans of the world and present complex life cycles with intermediate and definitive hosts. The genus is still poorly known, with an unstable taxonomy and, for most species, incompletely characterized geographical distributions. In this study, based on molecular and morphological evidence, we report that the species Profilicollis altmani is also distributed along the South American Atlantic coast, using the mole crab Emerita brasiliensis as an intermediate host. As such, our record shows that P. altmani has a Pan-American distribution where five species of Emerita are utilized as intermediate hosts.

Species within the Bemisia tabaci (Hemiptera: Aleyrodidae) complex in soybean and bean crops in Argentina.

The whitefly Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) is a cryptic species complex that contains some of the most damaging pests in tropical and subtropical regions. Recent studies suggested that this complex is composed of at least 24 distinct species. We use the approach from these studies to consider the identity of B. tabaci in Argentina. Previous studies have suggested the presence of a B. tabaci presumably indigenous to the Americas and referred to as the BR biotype in Argentina. We placed the entity referred to as the BR biotype within the B. tabaci cryptic species complex using whiteflies collected in soybean and bean crops in northern and central Argentina. The whiteflies were assigned using the mitochondrial cytochrome oxidase (mtCOI) gene. Four unknown haplotypes plus two Argentina sequences from GenBank formed a cluster that was basal to the rest of the New World sequences. These sequences diverged from the consensus sequence across the range of 3.6 to 4.3%. Applying the species assignment rules of recent studies suggests that the individuals from Argentina form a separate species. A fifth unknown haplotype fell within the New World putative species and formed a distinct cluster with haplotypes from Panama. These results suggest that Argentina has two indigenous species belonging to the B. tabaci cryptic species complex. Rather than using mtCOI sequencing for all B. tabaci collected, a simple random amplified polymorphic DNA-polymerase chain reaction diagnostic was used and tested along with previously published primers designed to work specifically with the BR biotype from Brazil. These primers were either unable to distinguish between the two indigenous members of the complex in Argentina or indicated a difference when none was evident on the basis of mtCOI sequence comparison.

Community-associated methicillin-resistant Staphylococcus aureus infections at an Army training installation.

To assess the burden of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) in a high-risk population, the monthly incidence of laboratory-confirmed MRSA in service members/trainees stationed at Fort Benning, Georgia, USA without hospitalization or surgery documented 30 days prior to infection was calculated for calendar years 2002-2007. Clinical management and antibiotic susceptibility patterns were also evaluated. By 2007, approximately 67% of S. aureus strains were MRSA, and approximately 82% of these were community-associated, primarily in trainees. In total, 3531 CA-MRSA infections were identified. Rates appeared to be seasonal, peaking at 42 cases/1000 soldiers in 2005, with rates remaining above 35/1000 soldiers thereafter. Increased prescription of effective antibiotics was documented. Susceptibility to clindamycin, ciprofloxacin, and levofloxacin decreased from 2002 to 2007 by 6%, 17%, and 14%, respectively. The sustained high prevalence of CA-MRSA observed highlights the need for more vigilant population-based counter-measures at military training installations.

Effects of short-term glucagon administration on gluconeogenic enzymes in the liver of midlactation dairy cows.

During lactation, the dairy cow experiences an increased demand for glucose to support milk production. Increased glucose demand can be met through increased capacity for gluconeogenesis, increased supply of glucose precursors, or a combination of both processes. Glucagon, a key hormone in glucose homeostasis, acts to promote gluconeogenesis and increase glucose output from liver. The objective of this study was to determine the effect of short-term administration of glucagon on expression of gluconeogenic enzymes in lactating dairy cattle. Sixteen multiparous Holstein cows were selected from the Purdue University Animal Sciences Dairy Research Center herd. Cows were stratified on the basis of milk production and days in milk and randomly assigned to either a saline or glucagon injection group (n = 8 per group). Cows were injected subcutaneously at -21, -14, -7, and 0 h relative to final glucagon and saline injections with either 3.75 mg of lyophilized bovine glucagon (15 mg/d) dissolved in 60 mL of 0.15 M NaCl (pH 10.25) or 60 mL of 0.15 M NaCl. Liver biopsy samples were obtained 1 wk before injection to establish baseline values and at 3 h after cows received final glucagon and saline injections. Biopsy samples were analyzed for mRNA abundance, enzyme activity, protein abundance, and in vitro measures of gluconeogenesis. Glucagon did not alter pyruvate carboxylase or cytosolic phosphoenolpyruvate carboxykinase (PEPCK) mRNA abundance, enzyme activity, or protein abundance, although there was a tendency for greater mRNA expression with the glucagon treatment (4.69 vs. 6.78, arbitrary units). Glucagon injections did not change mitochondrial PEPCK mRNA expression. Gluconeogenesis from 2.5 mM [2-(14)C]propionate and 2.0 mM [U-(14)C]lactate was similar in liver biopsy samples from glucagon-treated and control cows. There was no effect of glucagon on dry matter intake and milk production. Glucose, nonesterified fatty acids, beta-hydroxybutyrate acid, and insulin were not altered by glucagon. Blood glucagon was elevated, 76.09 vs. 96.14 pg/mL, for cows receiving glucagon injections. The data indicate that 24-h administration of glucagon does not alter cytosolic PEPCK mRNA expression or result in immediate alterations in total PEPCK enzyme activity and gluconeogenic capacity.

Isolation of shiga toxin-producing Escherichia coli from a South American camelid (Lama guanicoe) with diarrhea.

Shiga toxin-producing Escherichia coli belonging to serotype O26:H11 was isolated from a 2-month-old guanaco with severe watery diarrhea. E. coli colonies carried the stx1 and eae genes, showed localized adherence to HEp-2 cells, and produced enterohemolysin. A serological response to lipopolysaccharide O26 was observed at the onset of diarrhea.

Influence of abomasal carbohydrates on small intestinal sodium-dependent glucose cotransporter activity and abundance in steers.

Most animals adapt readily to increased supplies of carbohydrate in the intestinal lumen by increasing enzymes for degradation and increasing glucose transporter activity. However, the extent of upregulation of Na+-dependent glucose cotransporter 1 (SGLT1) activity and content in response to increased delivery of carbohydrate to the small intestinal lumen of ruminants is unclear. Therefore, an experiment was conducted to determine the effect of glucose and starch hydrolysate on the activity and abundance of SGLT1 in the small intestine of steers. In a randomized complete block design, 40 crossbred beef steers (243+/-2 kg BW) were fed 0.163 Mcal of ME/(kg BW0.75(d; W), 0.215 Mcal of ME/(kg BW0.75 x d; 2M), or 0.163 Mcal ME/(kg BW0.75 x d) and infused for 35 d into the rumen (R) or abomasum (A) with 12.6 g/(kg BW0.75 x d) of starch hydrolysate (S) or into the abomasum with 14.4 g/(kg BW0.75 x d) of glucose (G). Steers were slaughtered, and brush-border membrane vesicles were prepared from the small intestinal samples obtained from five equidistant sites along the intestine. Maltase activity in vesicles and homogenates differed with intestinal sampling site (quadratic, P < 0.001). Steers on the AG treatment yielded a greater intestinal maltase activity (38 nmol glucose x mg protein(-1) x min(-1)) compared with the AS, RS, W, or 2M treatments (34, 26, 23, and 23 nmol glucose x mg protein(-1) x min(-1) respectively [SEM = 3; P = 0.02]). Sodium-dependent glucose uptake averaged 18.4+/-3.94 pmol glucose/(mg protein x s) and was not affected by treatment, but uptake decreased distally along the intestine (P < 0.001). There was no effect of treatment on SGLT1 protein abundance, but SGLT1 protein abundance increased linearly from the duodenum to the ileum (P = 0.05). The inverse relationship between glucose uptake and SGLT1 abundance suggests that the regulation of brush border Na+-dependent glucose transport capacity is complex, involving factors other than the presence of luminal carbohydrate.

Non-O157 Shiga toxin-producing Escherichia coli isolated from diarrhoeic calves in Argentina.

Faecal samples from 76 diarrhoeic calves belonging to 36 farms located in the Pampas plain, Argentina, were examined for Shiga toxin-producing Escherichia coli (STEC). A total of 15 STEC strains were isolated from 12 (15.8%) calves which came from six different farms. All stx positive strains assayed by PCR were also positives in the Vero cell cytotoxicity test. The majority (60.0%) of the STEC strains carried the stx(1) gene. Twelve (80.0%) of the STEC isolates which belonged to serotypes O5:H- (n = 4), O26:H11 (n = 4), O26:H- (n = 1), O111:H- (n = 2), and O123:H38 (n = 1) were also enterohaemolysin (EHly) positive and carried the gene encoding for intimin (eae). All the stx positive strains were negative for the bfpA gene. Localized adherence to HEp-2 cells were observed in 83.3% of the eae+ STEC strains. STEC belonging to serotype O5:H- showed atypical biochemical properties, including urease production. Urease was also produced by two strains belonging to serotypes O153:H? and non-typeable, respectively. Resistance to three or more antibiotics was observed in 12 (80.0%) of the STEC isolates. Most of the serotypes of STEC recovered in this survey carried virulence traits that are associated with increased human and bovine pathogenicity. The present study shows that highly virulent STEC strains are being shed by diarrhoeic calves from farms located in a high incidence area of human STEC infections.

Occurrence and characteristics of CS31A antigen-producing Escherichia coli in calves with diarrhoea and septicaemia in Argentina.

CS31A is a K88-related non-fimbrial adhesin first described on Escherichia coli strains isolated from diarrhoeic and septicaemic calves. In this report, CS31A antigen was screened by immunological methods and confirmed by PCR among bovine E. coli isolates. In addition, CS31A-producing strains were characterized with respect to different fimbrial antigens, O-serogroup and other properties related to virulence. Faecal or tissue specimens of 100 diarrhoeic or septicaemic calves and 27 older cattle with different pathologies from 71 outbreaks or individual cases that occurred in Buenos Aires province, Argentina, were examined. CS31A + E. coli strains were isolated from 21 (21.0%) calves from 16 outbreaks or individual cases. No CS31A + E. coli was detected in samples from cattle more than 1 year old. Fimbriae F5, F41, F17a and F17b were not detected among the CS31A-producing strains. Three (14.3%) of the CS31A+ E. coli strains expressed the F17c fimbria. All of the 21 isolates exhibited at least one property of septicaemic strains (resistance to serum, production of aerobactin or colicins) but none of them demonstrated heat-stable enterotoxigenic activity. CS31A + E. coli isolates belonged to 10 serogroups, more commonly O8, O7, O17 and O21. The results obtained here confirm the worldwide distribution of CS31A antigen in bovine E. coli strains. However, CS31A + or CS31A + /F17c + E. coli were less frequently isolated than they were in North hemisphere countries.

Proteinase and gelatinolytic activities of house dust mite and cockroach extracts.

The presence of gelatinolytic activity in dust mite and Periplaneta americana allergenic crude extracts were studied. The former presented major activity in a broad band between 45 and 66 kDa and minor activity at 32 kDa, while the latter showed a more complex pattern with gelatinolytic activity at 90, 78, 65, 34, 32 and 24 kDa. When the proteolytic activity patterns of dust mites and cockroach crude extracts were analyzed at three different pH levels, the proteases in both cases were optimally active at pH 6, showed no activity at pH 3.5 and little activity at pH 8.5. The susceptibility of both extracts to a set of well-known protease inhibitors suggested that they are composed of cysteine and serine proteinases, the latter probably being a trypsin-like type. When immunochemical properties were studied, dust mite bands of about 200, 110, 65, 60 and 43 kDa showed immunoreactivity against a polyclonal human anti-dust mite serum, with the band of approximately 200 kDa presenting the highest antigenicity. A similar analysis was applied to the cockroach extract, which exhibited immunoreactive bands at 90, 78, 65 and 34 kDa when incubated with a polyclonal rabbit anti-Blatta serum. Only those of 90, 78 and 65 kDa reacted against a polyclonal human anti-Blatta serum. These results suggested a correlation between some proteases with gelatinolytic activity and the allergenicity of both extracts.

Hypersensitivity pneumonitis induced by Penicillium notatum antigens in guinea pigs.

Data concerning the experimental induction of hypersensitivity pneumonitis in guinea pigs using a glycoprotein derived from Penicillium notatum are presented. This antigen was obtained from the mycelial and metabolic products of the cultures passed through a Sephadex G-50 column. It was aerosolized for inhalation by adult guinea pigs for 12 weeks to detect specific serum IgM, IgG and IgE antibodies as well as sensitized leukotriene CD4 cells. Histopathological studies of the lungs showed interstitial infiltrates of macrophages and leukotriene cells, cellular bronchiolitis and single non-necrotizing granulomas. The results from this animal model suggest that this hypersensitivity pneumonitis is a typical delayed-type reaction due to chronic contact with the heterologous glycoprotein of Penicillium.

Bat feces as an indoor allergen.

We have demonstrated in an animal model (specific IgG) as well as in atopic patients suffering from rhinitis/asthma (specific IgE) that bat feces have antigenic properties. A single peak with high glycoprotein content was obtained by chromatography, while SDS-PAGE revealed several proteins between 29 and 116 kDa which showed immune serum blotting at 43.6 and 66 kDa. Positive specific skin tests with bat feces and IgE-RAST anti-bat feces were detected in atopic patients living in tall buildings and old houses in Buenos Aires. As bat feces did not cross-react with bat epithelium, studies evaluating rat serum and epithelium and pigeon feces in order to analyze the role of bat serum proteins, such as IgA, are encouraged.

Interstitial pneumonitis induced in guinea pigs by the antigens of Rhizopus nigricans.

Rhizopus nigricans (Rn) is one of the most common members of the Mucorales that produces opportunistic infections and hypersensitivity states. Data concerning experimental induction in guinea pigs of hypersensitivity pneumonitis with a glycoprotein antigen are presented. This antigen was obtained from the mycelial and metabolic products of the cultures and was aerosolized during 12 weeks. The presence of specific antibodies (IgG and/or IgE) was detected by serological techniques; histopathological studies of the lungs showed interstitial infiltrates of macrophages and LTCD8+ cells, as revealed by the MoAb used. Single non-necrotizing granulomas were characteristic from the tenth week to the end of the experiment. The results from this animal model suggest that hypersensitivity pneumonitis is a typical delayed-type reaction due to chronic contact with the heterologous glycoprotein of Rn. The relation of Rn antigen and the development of occupational diseases of the lung such as malt-worker's lung and wood-trimmer's disease is proposed and discussed.

Cross reactivity between the antigens of Periplaneta americana and Triatoma infestans.

The cockroach Periplaneta americana (Pa) and the reduviid Triatoma infestans (Ti) are two very common insects in Argentina that pollute indoor and outdoor environments. They are also strongly immunogenic in animals and in atopic men. Several immunological methods such as serological absorption procedures, diffusion gel methods and capillary electrophoresis were applied in order to establish the existence of common glycoprotein epitopes in the cockroach and in the reduviid. The presence of specific antibodies (IgG & IgE) were detected in rabbits as well as in human sera. The RAST and RAST-inhibition confirmed the cross-reactivity between these two antigens. Capillary electrophoresis evoked similar patterns among Pa, Ti and the moults of the nymphs of Ti. All these findings have clinical and epidemiological importance.