The tropical fowl mite, Ornithonyssus bursa (Acari: Macronyssidae): environmental and host factors associated with its occurrence in Argentine passerine communities.

The tropical fowl mite, Ornithonyssus bursa, is a common avian parasite found on diverse bird species worldwide. In the Neotropical region, O. bursa is present in wild birds, but it may also infect poultry and bite humans. Little is known about the ecology and epidemiology of this parasite. We conducted a thorough longitudinal study in passerine assemblages from central Argentina, gathering data from six reproductive seasons, with the aim of identifying factors that have a role in driving the occurrence and distribution of O. bursa in its natural hosts. We focused on the brood and microhabitat levels, accounting for potential confounders of higher levels. The results hereby presented contribute to our knowledge on the eco-epidemiology of O. bursa in natural hosts of the Neotropical region. Among the many variables assessed, nest material and host species appeared to be the most important correlates of O. bursa prevalence. Nonetheless, supplementary analyses showed that host species is a stronger predictor than nest material. Moreover, mite burden (parasite intensity) was found to depend on host species, but not on nest material. The association with species depended on nestling age, suggesting that resistance builds up as the nestling develop, but at a different pace depending on the bird species. Brood size was inversely correlated with intensity of parasitism, suggesting a dilution of the parasite burden on each nestling.

Dynamics of Exposure to Rickettsia parkeri in Cattle in the Paraná River Delta, Argentina.

Several cases of human rickettsiosis caused by Rickettsia parkeri were recently documented in the Paraná River delta of Argentina, where the tick vector is Amblyomma triste Koch. As cattle suffer recurrent A. triste infestations, they are at risk of becoming infected with R. parkeri Herein we investigated the dynamics of R. parkeri and its A. triste vector in a herd of beef cattle. Cattle were followed for 18 mo and samples were analyzed for the presence of antibodies against four Rickettsia species (R. parkeri, Rickettsia bellii, Rickettsia amblyommii, and Rickettsia felis) and also for the presence of rickettsial DNA. Additionally, cattle were examined for attached ticks and questing adult ticks were collected. All ticks were analyzed for the presence of rickettsial DNA. No evidence of rickettsemia was found in any cow, but the high R. parkeri infection rate documented in A. triste both questing in the study area (13.9%) and feeding on cattle (19.8%) and the identification of antibodies against R. parkeri antigen in 90% of cattle are evidence that infection is taking place. Altogether, our data suggest that A. triste ticks are capable of naturally exposing cattle to R. parkeri However, the progress of R. parkeri infection and its impact on bovine health and production remain to be established.

First record of the avian ectoparasite Philornis downsi Dodge & Aitken, 1968 (Diptera: Muscidae) in Argentina.

Species of Philornis Meinert, 1890 (Diptera, Muscidae) are Neotropical dipterans that include species with parasitic larvae which feed on nestling birds. To date, all Philornis species that have been recorded from Argentina have parasitic subcutaneous larvae. Here, for the first time for Argentina, we report the finding of Philornis downsi Dodge & Aitken, 1968, a fly with a nest-dwelling, semi-haematophagous larva. This record, from the humid Chaco ecoregion of Argentina in the nest of a saffron finch Sicalis flaveola pelzelni Sclater, substantially extends the known distribution of this species. We also report the consensus sequences of the internal transcribed spacer 1 (ITS1) and ITS2 regions of three of the specimens for future reference and comparison. Further investigation is needed to determine whether Argentina is part of the historical range of P. downsi or, alternatively, represents a recent expansion of its range, perhaps due to climatic changes or other factors of global environmental variation.