A cross‐sectional study of intestinal parasitoses in dogs and children of the periurban area of La Plata (Buenos Aires,Argentina): Zoonotic importance and implications in public health

A cross‐sectional study was performed between school term dates 2014 and 2015 to diagnose intestinal parasites in dogs and children living with them. The socio‐environmental characteristics and hygiene practices of the children were also evaluated in terms of risk factors for parasitic infection of periurban neighbourhoods of La Plata (Buenos Aires, Argentina). Serial coproparasitological samples of 78 dogs and 211 children were analysed by means of concentration and flotation techniques. Socio‐environmental variables and hygiene practices of children were evaluated through semi‐structured questionnaires which were answered by every family. The study showed that 82.1% of dogs were parasitized. The specific richness was of 11 species; Ancylostoma caninum (69.2%), Uncinaria stenocephala (41.0%), Trichuris vulpis (28.2%) and Toxocara canis (21.8%) were the most prevalent. The study also revealed that 67.8% of children were positive. Also, 11 species were identified and the most prevalent were Blastocystis sp. (36.0%), Enterobius vermicularis (27.5%) and Giardia lamblia (21.3%). The risk for parasitosis was higher in 6‐year‐old children and older (OR = 1.9, 95% IC: 1.0–3.7) and in those who did not wash their hands or did it occasionally after playing with their pets (OR = 2.8, 95% IC: 1.4–5.5). Blastocystis sp. and Entamoeba coli infection risks were greater in children whose parents had a basic level of education (OR = 3.4, 95% IC: 1.3–8.7 and OR = 3.6, 95% IC: 0.8–15.9, respectively). In addition, the risk of infection for E. coli was higher in children who lived in floodable houses (OR = 4.4, 95% IC: 0.9–16.6). Likewise, the risk of infection for E. vermicularis was greater in children with onychophagia (OR = 1.6, 95% IC: 0.7–3.7) and in 6 year olds and older whose parents completed only primary studies (OR = 3.6, 95% IC: 1.4–9.1). The results obtained show the existence of a worrying epidemiological scenario that stresses the importance of zoonotic parasitosis as a serious problem of public health.     

Phylogenetic divergence between Rickettsia amblyommatis strains from Argentina

The aim of this study was to investigate if there is a phylogenetic divergence of Rickettsia amblyommatis strains from different phytogeographic provinces of Argentina and South America. Therefore, ompA and ompB gene sequences of R. amblyommatis DNA detected in Amblyomma hadanii and Amblyomma neumanni ticks from the Yungas and Chaco phytogeographic provinces, respectively, were obtained. These sequences were compared with GenBank sequences from R. amblyommatis from different countries of the American continent. The analyses shown that ompA haplotypes of R. amblyommatis form two clusters which differ phylogenetically. Regarding to ompB sequences, three groups of R. amblyommatis strains were detected. It could be shown that strains of R. amblyommatis detected in A. hadanii from the phytogeographic province Yungas are phylogenetic different to them detected in A. neumanni from the phytogeographic province Chaco. Furthermore, it could be observed that strains detected in different tick species associated with different phytogeographic provinces of the American continent differ phylogenetically.     

Flood pulse and the dynamics of fish assemblage structure from neotropical floodplain lakes

Abstract – The dynamics of fish assemblages from seven floodplain lakes of Salado River (Argentina) was monthly analysed during two contrasting hydrological seasons. Partial canonical correspondence analysis indicated that assemblage structure was predictably linked to environmental characteristics that varied along temporal and spatial scales. Species distributed differentially along an environmental gradient of temperature, hydrometric level, conductivity, macrophyte cover and transparency in relation to their sensory capabilities (following piscivory‐transparency‐morphometry model) and life history strategies. During high water season, assemblages were associated with temperature and hydrometric level, factors which varied mainly across temporal scales and exhibit a regional range of action. During low waters, assemblage structure correlated with macrophyte cover and transparency, factors that varied fundamentally on spatial scales and have local impact. These results indicate that the determinism of fish assemblages does not vary substantially between hydrometric periods, although the environmental variables affecting fish assemblages and their scale of action are clearly different.     

2012年阿根廷农药市场研究及启示

本文研究了2012年阿根廷农药市场的特点,分析了阿根廷农药市场的发展趋势,提出了我国新农药产品研发的意见建议。     

Cryptosporidium parvum GP60 subtypes in dairy cattle from Buenos Aires,Argentina

Cryptosporidium parvum from 73 dairy calves less than two months old from Buenos Aires province (Argentina) were molecularly characterized using sequence analysis of the GP60 gene. Seventy-five sequences were obtained, and seven different subtypes were identified, all belonging to the IIa subtype family. The most common subtypes were IIaA20G1R1 (27/75), IIaA22G1R1 (16/75), and IIaA18G1R1 (13/75). Subtypes IIaA21G1R1, IIaA23G1R1, IIaA16G1R1 and IIaA19G1R1 were found sporadically. Two samples contained mixed infections with IIaA21G1R1 and IIaA22G1R1. A significant association was found between subtypes and geographic location, whereas there was no relation between subtypes and presence of diarrhea. Three of the subtypes found in this study (IIaA16G1R1, IIaA18G1R1, and IIaA19G1R1) were previously identified in humans. These findings suggest that cattle could play an important role in the transmission of cryptosporidiosis to humans in Buenos Aires province.     

First report of BVDV circulation in sheep in Argentina

Pestiviruses are capable of infecting a wide range of animals within the order Artyodactila. Currently, the genus Pestivirus includes Bovine Viral Diarrhea Virus 1 (BVDV-1) and 2 (BVDV-2), Border Disease Virus (BDV), and Classical Swine Fever Virus (CSFV). BVDV-1, BVDV-2 and BDV are able to cross species barrier to infect a wide range of hosts, whereas CSFV is restricted to domestic pigs and wild boars. In Argentina, 70% of cattle are seropositive to BVDV. Although there were some serological studies in llamas, alpacas and buffaloes, no reports existed about the circulation of BVDV in sheep in Argentina. Based on these, 54 blood samples of healthy ovines were analysed by serology. The results showed that 46.3% of the analysed sheep were seropositive to BVDV-1, 13% to BVDV-2 and 20.4% for both BVDV-1 and BVDV-2. The molecular analysis confirmed the presence of BVDV-1a in some samples.     

The sustainability of subsistence hunting of peccaries in the Argentine Chaco

Subsistence hunting practiced by poor rural and indigenous people in Latin America differentially affects the three species of peccaries (Artiodactyla: Tayassuidae). Sustainability of subsistence hunting of peccaries in the Argentine semi-arid Chaco, where the three species coexist, was unknown. My objectives were to determine the importance of peccaries for the local people, describe the current pattern of hunting and its impact on the three species of peccary and identify the factors that affect hunting sustainability. I found that many rural (70%) and village people (40%) consumed peccaries. White-lipped and chacoan peccaries were more susceptible to overharvesting than collared peccary. Current rates of hunting of white-lipped and chacoan peccaries are likely not sustainable because: (a) density of both species was between two to three times higher inside a protected area than outside; (b) populations have declined near larger villages and in older settlements; (c) herds sizes were small in comparison with other regions; (d) large number of juveniles less than one year old were harvested; (e) hunting did not discriminate based on sex or reproductive status and (f) The unified harvest model indicated unsustainable harvest because more than 40% of the reproductive production was taken and populations densities were less than 60% carrying capacities. In contrast, harvest of collared peccary seems sustainable at the current rates of hunting by rural peasants. Other threats such as forest exploitation, however, are accelerating, and are likely to reduce sustainability.     

Host range study of Argentine Nacobbus aberrans sensu Sher populations and comments on the differential host test

The existence of races within the species Nacobbus aberrans sensu Sher has been confirmed; however, there is no consensus on a consistent system for race determination. Four plant species previously used as differential hosts in some N. aberrans race tests (tomato, pepper, sugarbeet and potato) were tested for susceptibility to seven nematode populations from Argentina. Plants were inoculated with second-stage juveniles and kept under glasshouse conditions at 21 °C for 90 days. The parameters evaluated (root gall index, egg mass index, and reproduction factor) in different nematode populations and plants showed significant differences. The reproductive fitness of the nematode populations differed among the plants that showed some degree of susceptibility. The results showed that N. aberrans comprises populations differing in host preference. Based on the nematode populations’ behaviour on these hosts, two groups were distinguished: i) populations that multiplied on all hosts, ii) populations that did not multiply on potato. The present work contributes to the analysis of criteria for developing a differential host test.     

Carbon contents and aggregation related to soil physical and biological properties under a land-use sequence in the semiarid region of central Argentina

Land-use change affects vast areas of the semiarid region of central Argentina, where agriculture becomes predominant over mixed farming systems, and large areas of permanent pastures (PAS) are being converted to agricultural land. This land-use change causes loss of soil structure, but very little is known about the effect of changes in aggregate size distribution on soil physical, chemical and biological properties. We decided to use dry sieved aggregates since this technique is commonly used in semiarid regions. The study was carried out at Anguil, La Pampa, Argentina. The soil was a sandy loam Entic Haplustoll with a carbonate-free A-horizon. The PAS site had been under weeping love grass for more than 40 years. Parts of this PAS were turned to cultivation in 1989 (CULT14) and in 2001 (CULT2). Sampling was carried out at 0.6 m intervals to 0.18 m depth. Bulk density (BD), organic carbon (OC), and water holding capacity and infiltration were determined on these samples. Dry aggregate size distribution and OC content of the size fractions were determined on large undisturbed samples. Samples of pooled aggregate size fractions >4, 1–4, and <1 mm, as well as corresponding samples of non fractionated soil were incubated and respiration was measured by CO₂ evolved. The soil of CULT2 had 29% lower contents of large (>4 mm) and 37% higher contents of very small (<1 mm) aggregates than PAS. The intermediate size aggregates were not affected by the short-term effect of tillage. OC loss in CULT2 was 16% regarding PAS. Longer term effects of cultivation were characterized by 30% loss of intermediate size aggregates, 22% increase of bulk density, 74 and 19% decrease in water infiltration and water retention, respectively of CULT14 compared to PAS. A 32% decrease of OC was observed after 14 years of cultivation. Intermediate size aggregates had highest OC contents and no difference between treatments was found, except for a lower value of large aggregates in CULT14. Respiration rates and total CO₂ evolved was related to OC contents of fractions; however, PAS respired more from its small aggregates than expected from their OC content. The results showed that OC turnover and loss of aggregation was very fast in this soil, but soil hydraulic properties were affected in the longer term. Dry aggregates were found to useful for studying soil degradation, and they showed similar trends as those indicated in the literature for water stable aggregates.