M. Mónica Díaz

Leptospirosis: a zoonotic disease of global importance

In the past decade, leptospirosis has emerged as a globally important infectious disease. It occurs in urban environments of industrialised and developing countries, as well as in rural regions worldwide. Mortality remains significant, related both to delays in diagnosis due to lack of infrastructure and adequate clinical suspicion, and to other poorly understood reasons that may include inherent pathogenicity of some leptospiral strains or genetically determined host immunopathological responses. Pulmonary haemorrhage is recognised increasingly as a major, often lethal, manifestation of leptospirosis, the pathogenesis of which remains unclear. The completion of the genome sequence of Leptospira interrogans serovar lai, and other continuing leptospiral genome sequencing projects, promise to guide future work on the disease. Mainstays of treatment are still tetracyclines and beta-lactam/cephalosporins. No vaccine is available. Prevention is largely dependent on sanitation measures that may be difficult to implement, especially in developing countries.

Human leptospirosis caused by a new, antigenically unique Leptospira associated with a Rattus species reservoir in the Peruvian Amazon.

As part of a prospective study of leptospirosis and biodiversity of Leptospira in the Peruvian Amazon, a new Leptospira species was isolated from humans with acute febrile illness. Field trapping identified this leptospire in peridomestic rats (Rattus norvegicus, six isolates; R. rattus, two isolates) obtained in urban, peri-urban, and rural areas of the Iquitos region. Novelty of this species was proven by serological typing, 16S ribosomal RNA gene sequencing, pulsed-field gel electrophoresis, and DNA-DNA hybridization analysis. We have named this species “Leptospira licerasiae” serovar Varillal, and have determined that it is phylogenetically related to, but genetically distinct from, other intermediate Leptospira such as L. fainei and L. inadai. The type strain is serovar Varillal strain VAR 010T, which has been deposited into internationally accessible culture collections. By microscopic agglutination test, “Leptospira licerasiae” serovar Varillal was antigenically distinct from all known serogroups of Leptospira except for low level cross-reaction with rabbit anti–L. fainei serovar Hurstbridge at a titer of 1∶100. LipL32, although not detectable by PCR, was detectable in “Leptospira licerasiae” serovar Varillal by both Southern blot hybridization and Western immunoblot, although on immunoblot, the predicted protein was significantly smaller (27 kDa) than that of L. interrogans and L. kirschneri (32 kDa). Isolation was rare from humans (2/45 Leptospira isolates from 881 febrile patients sampled), but high titers of MAT antibodies against “Leptospira licerasiae” serovar Varillal were common (30%) among patients fulfilling serological criteria for acute leptospirosis in the Iquitos region, and uncommon (7%) elsewhere in Peru. This new leptospiral species reflects Amazonian biodiversity and has evolved to become an important cause of leptospirosis in the Peruvian Amazon.

First results on the water chemistry, algae and trophic status of an Andean acidic lake system of volcanic origin in Patagonia (Lake Caviahue)

The acidic caldera lake Caviahue (Patagonia, Argentina) and its main tributaries were studied on two dates during September 1998. The main results are: The acidity of the Lake Caviahue (pH: 2.56, acidity: >5 mmol H+ l−1) is controlled by the extremely acidic Upper Rio Agrio (pH: 1.78, acidity: >20 mmol H+ l−1). The high sulphate contents of both the river and the lake can be attributed to sulphuric acid generated by the uptake of sulphurous gases in the crater lake of Copahue Volcano at approximately 2800 m a.s.l. The high concentrations of both Fe and trace metals (e.g. Cr, Ni, Zn) in Lake Caviahue originate from sulphur–acid interactions with the predominantly volcanic geology of the catchment area. The P-rich andesitic geology influences both the Upper and Lower Rio Agrio and Lake Caviahue. Both were found to have high phosphorus concentrations (300–500 μg P l−1) indicative of a high potential for eutrophication. The plankton community consisted of bacterioplankton, phytoplankton and rotifers. The phytoplankton was dominated by one green alga, Keratococcus raphidioides (>90% of total abundance) followed by a green sphaerical and Chlamydomonas sp. The total phytoplankton density was about 15 000 cells ml−1 in the upper 10 m of the water column. Rotifers were represented by one bdelloid species and their abundance was highly variable (360–4040 ind l−1) in the water columm. In the Upper and Lower Rio Agrio, the epilithic community was dominated by one chloroccocal species and two species of Ulothricales. According to trophic categories based on phytoplankton density and TP concentration, Lake Caviahue can be classified as mesotrophic/eutrophic. However, chlorophyll a concentrations observed were not in agreement with this state.

Phytoplankton of two Araucanian lakes of differing trophic status (Argentina)

The Araucanian lake district in southern South America encompasses many great lakes of glacial origin, as well as a large number of smaller lakes. In this study, we present data on two waterbodies, one large (Nahuel Huapi), and one shallow (Verde). The phytoplankton community structure and dynamics or either lake were monitored for a year, in relation to the physical and chemical fluctuation, as well as the morphometry of the respective basins. In the large lake, the phytoplankton biomass was strongly dominated by diatoms (Aulacoseira granulata, Rhizosolenia eriensis and Cyclotella stelligera) and by dinoflagellates (Gymnodinium and Peridinium spp.). In the small lake, Verde, the dominant algae were Trachelomonas spp. and Cosmarium punctulatum, during the summer biomass maximum, and Rhodomonas lacustris, Chrysochromulina parva and Navicula spp. during autumn. The maximum biomass value was 634 mg m-3 in Lake Nahuel Huapi in spring and 7800 mg m-3 in Lake Verde in summer. According to their phytoplankton and physical and chemical features, Lakes Nahuel Huapi and Verde are readily classifiable, as ultra-oligotrophic and mesotrophic, respectively.

A NEW SPECIES OF GRACILE MOUSE OPOSSUM, GENUS GRACILINANUS (DIDELPHIMORPHIA: DIDELPHIDAE), FROM ARGENTINA

Abstract A new species in the genus Gracilinanus is described on the basis of a specimen found in a museum collection. The new species is known only from the type locality, which is located in the Yungas phytogeographic province near the Parque Nacional Calilegua, Jujuy Province, Argentina. Presently, the area is highly disturbed because of agricultural activity, mainly the cultivation of sugar cane. External, dental, and cranial morphology are described, and morphometric data as well as comparisons with other species in the genus Gracilinanus are presented.

A new species of Akodon (Muridae: Sigmodontinae) from Northwestern Argentina.

A new species of Akodon is described using cranial, dental, and external morphology and morphometric data. The new species inhabits an isolated, ecotonal, montane forest-grassland area in central Tucuman Province, Argentina. This species, which appears to be closely related to A. puer caenosus , is here included in the boliviensis group of akodont rodents. Comparisons are made with A. spegazzinii and A. puer caenosus , which are found in the general area and are of similar body size and general morphology.

Fleas Associated with Mammals from Northwestern Argentina, with New Distributional Reports

Abstract Northwestern Argentina is an area of a high biodiversity. However, few fleas have been recorded parasitizing mammals. In the present study we report the results of surveys carried out in the provinces of Salta, Jujuy, Tucumán, and Catamarca. The following 9 flea species and subspecies were collected from 17 species of mammals: Craneopsylla minerva minerva (Rothschild, 1903) (Stephanocircidae); Neotyphloceras crassispina hemisus Jordan, 1936 (Ctenophthalmidae); Adoratopsylla (Tritopsylla) intermedia intermedia (Wagner, 1901) (Ctenophthalmidae); Tetrapsyllus (Phylliver) bleptus (Jordan and Rothschild, 1923) (Rhopalopsyllidae); Polygenis (Polygenis) acodontis (Jordan and Rothschild, 1923) (Rhopalopsyllidae); Phthiropsylla agenoris (Rothschild, 1904) (Malacopsyllidae); Malacopsylla grossiventris (Weyenbergh, 1879) (Malacopsyllidae); Pulex irritans Linnaeus, 1758 (Pulicidae); and Hectopsylla gracilis Mahnert, 1982 (Tungidae). Neotyphloceras crassispina hemisus, Ad. (T.) i. intermedia, Ph. agenoris, and H. gracilis are reported for the first time from northwestern Argentina, from specimens collected in the provinces of Jujuy, Salta, and Catamarca. The mammals Micoureus constantiae (Thomas, 1904); Thylamys cf. cinderella (Thomas, 1902); Thylamys sponsorius (Thomas, 1921) (Didelphimorphia); Akodon albiventer Thomas, 1897; Akodon caenosus Thomas, 1918; Calomys lepidus (Thomas, 1884); Eligmodontia hirtipes Thomas, 1902; Eligmodontia puerulus (Philippi, 1896); Phyllotis xanthopygus (Waterhouse, 1837); Tapecomys primus Anderson and Yates, 2000 (Rodentia); and Chaetophractus vellerosus (Gray, 1865) (Cingulata) have an increased number of parasite species known to them. Eighteen new parasite–host associations are also reported.

Tick collections from the Peruvian Amazon, with new host records for species of Ixodes Latreille, 1795 (Acari: Ixodidae) and Ornithodoros Koch, 1844 (Acari: Argasidae)

Abstract Tick-infested bats, rodents and marsupials were captured along the Iquitos-Nauta highway, Loreto Department, in the Peruvian Amazon. The only ticks found on Chiroptera were members of the Ornithodoros hasei (Schulze, 1935) species group, collected from Noctilio albiventris Desmarest, 1818, Rhinophylla pumilio Peters, 1865 and Myotis albescens (É. Geoffroy, 1806). Rhinophylla pumilio is a new host and M. albescens was confirmed as a host for the O. hasei group. Among Rodentia, Oecomys bicolor (Tomes, 1860), Oligoryzomys microtis (Allen, 1916), Hylaeamys perenensis (Allen, 1901) and Hylaeamys yunganus (Thomas, 1902) were infested with larvae (O. bicolor) or nymphs (other three rodents) of Ixodes luciae Sénevet, 1940; all are new hosts for I. luciae. Tick infestation was more diverse among the Didelphimorphia, where a nymph and larva of Amblyomma sp. were collected on Philander opossum (Linnaeus, 1758), a nymph of Amblyomma sp. on Caluromys lanatus (Olfers, 1818), and a larva of Ixodes pararicinus Keirans & Clifford, 1985 on Monodelphis adusta (Thomas, 1897). Monodelphis adusta is a new host for I. pararicinus. Caluromys lanatus, Marmosops sp., Metachirus nudicaudatus (Desmarest, 1817), Micoureus sp., Philander andersoni (Osgood, 1913) and P. opossum were parasitized with larvae (Micoureus sp.) or adults (all other didelphids) of I. luciae. With the exception of P. opossum, all these marsupials are new hosts for I. luciae.

The Ornithodoros hasei (Schulze, 1935) (Acari: Argasidae) species group in Argentina

Abstract Six larvae of the genus Ornithodoros were collected in Rio Lavayén, approximately 1km north of Santa Rita, San Pedro Department (24° 28′S, 64° 48′W), Jujuy Province, Argentina, on three species of bats: Molossops temminckii (Burmeister, 1854) (Molossidae), Myotis albescens (E. Geoffroy, 1806) (Vespertilionidae) and Histiotus laephotis Thomas, 1916 (Vespertilionidae). All six larvae were identified as belonging to the Ornithodoros hasei species group, whose members are common parasites of bats throughout the Neotropical Zoogeographic Region. This is the first record of the O. hasei species group in Argentina, and M. temminckii and H. laephotis are new hosts for this tick. Studies of the morphology, genetics and ecology of O. hasei across its vast range will be necessary in order to determine whether sibling species are present.

First record of the invasive algae Didymosphenia geminata in the Lake Nahuel Huapi: Argentina, Patagonia

Fil: Beamud, Sara Guadalupe. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Patagonia Norte. Instituto de Investigacion en Biodiversidad y Medioambiente; Argentina