Trichurid nematodes from South American Camelid: an approach to native assemblages through the parasitology of archaeological sites.

To gain insights into the trichurid diversity in pre-Hispanic remains of South American camelids (SACs), as well as into modern SAC populations, a bibliographic search was carried out to find parasitological studies. Results showed that a total of 17 studies were performed at archaeological and paleontological sites, in which a total of 213 samples were examined. The sample set was used as the unit of analysis, and 83% of 52 pre-Hispanic sample sets were positive for parasites. Parasitological studies confirmed the pre-Hispanic presence of diverse trichurids: two Trichuris species and capillariid eggs with morphological differences that allowed them to be assigned to three different species. Currently, the richness of the native trichurid assemblages in SACs has been extended by the inclusion of two species (Trichuris sp. 2 and Capillariinae gen. sp. 1). Modern T. tenuis Chandler, 1930, considered SAC-specific, would have invaded SAC populations during the European colonization. The estimate of regional and temporal trichurid prevalence and paleoecological information allowed us to propose a possible origin for some of them. Although the present analysis is exploratory, it should stimulate future studies about the biogeographic history of SAC helminths, provide relevant information to improve descriptions of the Holocene ecology, and identify threatened helminths.

Lamanema chavezi (Nematoda: Molineidae): epidemiological data of the infection in South American camelids of Northwest Argentina.

Faecal samples from llamas (n=708), vicuñas (n=171) and guanacos (n=4) were obtained between December 2004 and May 2009 in three Provinces of Northwest Argentina (Jujuy, Salta and Catamarca) to know the distribution, prevalence and intensity of Lamanema chavezi infection in these South American camelid species (SACs). Faeces were examined by a sedimentation-flotation technique using a Cl(2)Zn+ClNa solution (specific gravity=1.59). Eggs of L. chavezi occurred in 30.3% of 89 llama herds and in 18.5% of 708 llamas sampled with a mean intensity of 271.8 eggs/g (EPG) of faeces (range 20-2120). The highest values for all parameters of the infection were registered in llamas from Catamarca Province. Significant differences (P<0.001, Fisher's exact test) were detected only for the lower prevalence in llamas from Jujuy respect to those from the other two Provinces. The overall individual prevalence of L. chavezi in llamas was lower than in reports from adult domestic camelids of neighbour countries while mean intensity was higher. The individual prevalence of L. chavezi in guanacos was 75.0%, with a mean intensity of 66.0 EPG (range 40-120) while no vicuñas were detected as infected. Most of infected SACs were located at the phytogeographical region of Andean Patagonic Domain with a dispersion ranging between 22 degrees 10' and 26 degrees 40' South latitude.

Prevalence of Eimeria macusaniensis and Eimeria ivitaensis in South American camelids of Northwest Argentina.

Faecal samples from mostly adult llamas (n=626), vicuñas (n=161) and guanacos (n=4) were obtained between December 2004 and July 2008 in three Provinces of Northwest Argentina in order to study the prevalence of Eimeria macusaniensis and Eimeria ivitaensis. Faeces were examined by a flotation technique using a Cl(2)Zn+ClNa solution (specific gravity=1.59). Oocysts of E. macusaniensis occurred in 88.3% of 77 llama herds and in 50.3% of 626 llamas sampled whereas oocysts of E. ivitaensis occurred in only four llamas (herd and llama prevalence of 5.2% and 0.6%, respectively). The individual prevalence of E. macusaniensis in vicuñas and guanacos were of 14.3% and 25.0%, respectively. E. ivitaensis was not detected in these latter species. The results showed a prevalence of E. macusaniensis higher than previously reported in adult domestic camelids (llamas and alpacas). In contrast, the very low prevalence of E. ivitaensis in llamas and its absence in wild camelids (vicuñas and guanacos) was remarkable. Differences between prevalence of both coccidian species are discussed.

Amblyomma tigrinum (Acari: Ixodidae): new data on hosts and biology of immature stages and on DNA composition.

Biological data of immature stages of Amblyomma tigrinum were obtained from larvae and nymphs both fed on rats and rabbits. Data from nymphs recovered from a wild rodent (Galea musteloides) are also reported. Additional results in DNA composition of males moulted from nymphs fed on laboratory and wild hosts are presented. The ticks were maintained in darkness at 27 +/- 1 degrees C and 83-86% RH. The mean recovery rates were 49.1% and 43.6% with a moulting success of 96.2% and 90.8% in larvae fed on rats and rabbits, respectively. The engorgement weights were almost identical in larvae recovered from both hosts. The mean recovery rates of nymphs were 37.3% and 69.9% in specimens fed on rats and rabbits, respectively. The moulting success was 94.5%, 100% and 98.1% in nymphs fed on rats, rabbits and G. musteloides, respectively. Nymphs from all hosts moulting to females were significantly heavier (P < 0.01) than those moulting to males despite their range of engorgement weight showed overlap. A higher proportion (>or=61.5%) of nymphs from all hosts moulted to females. Present results suggest that members of Rodentia and Lagomorpha are suitable hosts for the immature stages of A. tigrinum, contrasting with previous results from Brazilian colonies of this tick. The DNA sequence from ticks fed on G. musteloides showed 99.7% identity with that from ticks fed on rabbits and also with the DNA sequence already available (GenBank AY498562 ) for A. tigrinum.

Eprinomectin pour-on for control of Boophilus microplus (Canestrini) ticks (Acari: Ixodidae) on cattle.

The efficacy of a commercial pour-on formulation of eprinomectin, a macrocyclic lactone, against experimental infestations of Boophilus microplus (Canestrini) ticks was evaluated in two trials involving 27 Bos taurus calves. The first trial was designed to evaluate the effects of a single treatment at a dose of 0.5 mg/kg of body weight against standard size B. microplus females (4.5-8.0 mm long). A significant reduction in tick numbers (P<0.05, Wilcoxon test) was observed between treated calves as compared to untreated ones from Day 3 (44% efficacy) after treatment to the end of the trial on Day 28 (96.9%), with a peak efficacy of 97.1% on Day 21. In the second trial the effect of eprinomectin on standard size tick numbers, engorgement weight and fertility of female ticks from calves with a single treatment dose of 1 mg/kg on Day 0 and calves treated twice at a dose of 0.5 mg/kg on Days 0 and 4 was evaluated. An efficacy >93% was obtained from Day 2 to Day 28 after treatment in calves treated twice at 0.5 mg/kg, and to the end of the trial (Day 35) in calves treated once with 1 mg/kg. The 1mg/kg treatment provided >98% residual efficacy for at least 7 days. During the first part of the second trial the efficacy of eprinomectin resulted from a dramatic adverse effect on engorgement weight and fertility of female ticks, with 100% control on Day 5 (dosage of 1 mg/kg) and on Days 6 and 7 (two doses of 0.5 mg/kg). Following Day 7, most of the effect was due to reduction in the number of standard size female ticks.

First report of Lamanema chavezi (Nematoda: Trichostrongyloidea) in llamas (Lama glama) from Argentina.

Lamanema chavezi is a characteristic helminth of llamas and alpacas in Peru and Chile. However, its overall geographic range has not been well defined. This report documents the presence of L. chavezi in llamas from Argentina.

Susceptibility to two pyrethroids in Boophilus microplus (Acari: Ixodidae) populations of northwest Argentina. Preliminary results.

Cattle are treated 6-12 times yearly to control Boophilus microplus ticks in the east zone of the Argentinean infested region, while 1-4 treatments are applied for tick control in the west zone. In the 1970s resistance to organo-phosphate acaricides was found in the east zone, but not in the west zone. However, a shift to synthetic pyrethroids (SP) was made through all infested regions. Currently, indications of resistance to SP in the east zone, but not in the west zone, are provoking to a switch to formamidine acaricides. During 1998 a total of 147 B. microplus engorged females were collected from 20 beef cattle ranches from the west zone of the Argentinean infested region. Individual progenies of these ticks were tested ('larval packet test') with cypermethrin and deltamethrin, and their LC 50 and LC 90 were compared to those estimated for the Milagro susceptible strain. No evidence of resistance to these SP was found. Due to sampling restraints the results are presented as preliminary. Nevertheless, a shift away from use of SP for control of B. microplus in the west zone appears to be unjustified and should be independent of the resistance circumstances observed in the east zone of the Argentinean tick infested region.

Experimental infestation of llamas (Lama glama) with Boophilus microplus (Acari:Ixodidae).

Two llamas (Lama glama) were infested with approximately 20,000 Boophilus microplus larvae each and maintained under controlled conditions to collect the detached adult ticks. A total of 72 engorged and semi-engorged females were recovered with a mean weight of 163.0 +/- 70.6 mg. Sixty-three (87.5%) of these ticks oviposited and 60 (95.2%) of the egg masses produced larvae. Six of the heaviest females laid 18,838 eggs from which 16,545 (87.8%) hatched. These results show that llamas are able to maintain a population of B. microplus under experimental conditions. Further studies are required to determine the role of llamas as alternative hosts for B. microplus under field conditions.

Recovery of Trichuris tenuis Chandler, 1930, from camelids (Lama glama and Vicugna vicugna) in Argentina.

A survey of whipworms was conducted in llamas and vicuñas in northwestern Argentina. Fecal examinations of a group of 14 llamas (April 1995-March 1996) and 69 vicuñas (November 1996) indicated a high prevalence (usually >50%) of Trichuris sp. in these hosts. Prevalence was highest during July-November 1995 that also coincided with the highest mean fecal egg count. During postmortem examinations of 1 llama and 1 vicuña, specimens of Trichuris tenuis were recovered from the cecum/large intestine of each camelid. This is the first report of T. tenuis in South America, and the first report in the vicuña. It is suggested that T. tenuis is the typical whipworm of aboriginal camelids.

First detection of Argas (Argas) neghmei (Acari: Argasidae) in Argentina.

Attacks by adult stages of the soft tick Argas (Argas) neghmei (Acari: Argasidae) on inhabitants of the High Andean plateau of Argentina are reported. This is the first local report of this species, which was previously found in the north of Chile. Taxonomic differences between A. (A.) neghmei and other neotropical and exotic species of the genus are underlined. The status of the knowledge about the Argentine argasid fauna is briefly described.

Some quantitative aspects of natural babesial infection in the haemolymph of Boophilus microplus engorged female ticks.

Quantitative aspects of the natural babesial (Babesia bovis and Babesia bigemina) infection in Boophilus microplus engorged female ticks obtained from two herds of Holstein heifers positive by the immunofluorescent antibody test to both protozoan were evaluated. The number of kinetes/microscope field of haemolymph was determined for each tick from day 5 to 10 post-collection. A close relationship between daily and cumulative babesial infection was detected. Correlation and determination coefficients between days post-collection and the daily and cumulative infection rates, including heavily infected ticks (those ticks carrying at least 3.0 kinetes/microscope field of haemolymph), were always higher than 0.9 (P < 0.01) in ticks of both herds. The median was found to be a more representative measure than the mean to define the distribution of kinetes number amongst infected ticks since this is a negative binomial distribution. The analysis of the sequential order of days of infection more accurately showed the amplification of the babesial infection in the tick haemolymph than the evolution of kinetes number in relation to days post-collection. Sampling ticks on days 8, 9 and 10 post-collection would have detected all ticks infected with Babesia spp. from both herds. A categorization of infected or non infected ticks would be of greater epidemiological importance than the haemolymph infection level, based upon previous laboratory studies that showed a poor relationship between haemolymph infection in the female ticks and the infection rate in their eggs. However, further studies in natural infected ticks and better techniques to differentiate B. bovis and B. bigemina kinetes are needed before these laboratory results can be applied to field conditions.

Experimental studies of the rate of infection of Boophilus microplus eggs with Babesia bovis.

Babasia bovis infection in the eggs of Boophilus microplus was investigated by examining the total output of eggs by 10 engorged female ticks with a level of haemolymph infection with B bovis ranging from 0.2 to 20.6 kinetics per microscope field. The ticks were fed on infected calves, with a parasitaemia ranging from 0.01 per cent to 0.02 per cent, inoculated with a stabilate of B microplus larvae containing the protozoa. Infected eggs, 9.5 per cent of the total eggs laid, were detected from the fourth day of oviposition onwards. No relationship was found between the level of haemolymph infection and the percentage or total number of infected eggs laid.

Evaluation of the infectivity of a vaccinal and a pathogenic Babesia bovis strain from Argentina to Boophilus microplus.

Three trials were performed to test the infectivity of a vaccinal and a pathogenic strain of Babesia bovis for the tick Boophilus microplus. The progeny of engorged female ticks fed on calves inoculated with the pathogenic strain were able to transmit the infection to splenectomised calves (measured by the presence of the parasite in their blood and seroconversion), whereas the progeny of engorged females fed on calves inoculated with the vaccinal strain did not transmit the organisms. These results appear to show that this strain of Babesia bovis would not be transmitted by ticks under natural conditions. This is a considerable advantage since the organisms used in the vaccine would not be able to establish foci in the field although they would be able to confer a long-lasting immunity.