Artur Kanadani Campos

Geographical distribution of Amblyomma cajennense (sensu lato) ticks (Parasitiformes: Ixodidae) in Brazil, with description of the nymph of A. cajennense (sensu stricto)

BackgroundUntil recently, Amblyomma cajennense (Fabricius, 1787) was considered to represent a single tick species in the New World. Recent studies have split this taxon into six species. While the A. cajennense species complex or A. cajennense (sensu lato) (s.l.) is currently represented by two species in Brazil, A. cajennense (sensu stricto) (s.s.) and Amblyomma sculptum Berlese, 1888, their geographical distribution is poorly known.MethodsThe distribution of the A. cajennense (s.l.) in Brazil was determined by morphological examination of all lots of A. cajennense (s.l.) in two large tick collections of Brazil, and by collecting new material during three field expeditions in the possible transition areas between the distribution ranges of A. cajennense (s.s.) and A. sculptum. Phylogenetic analysis inferred from the ITS2 rRNA gene was used to validate morphological results. Morphological description of the nymphal stage of A. cajennense (s.s.) is provided based on laboratory-reared specimens.ResultsFrom the tick collections, a total 12,512 adult ticks were examined and identified as 312 A. cajennense (s.s.), 6,252 A. sculptum and 5,948 A. cajennense (s.l.). A total of 1,746 ticks from 77 localities were collected during field expeditions, and were identified as 249 A. cajennense (s.s.), 443 A. sculptum, and 1,054 A. cajennense (s.l.) [these A. cajennense (s.l.) ticks were considered to be males of either A. cajennense (s.s.) or A. sculptum]. At least 23 localities contained the presence of both A. cajennense (s.s.) and A. sculptum in sympatry. DNA sequences of the ITS2 gene of 50 ticks from 30 localities confirmed the results of the morphological analyses. The nymph of A. cajennense (s.s.) is morphologically very similar to A. sculptum.ConclusionOur results confirmed that A. cajennense (s.l.) is currently represented in Brazil by only two species, A. cajennense (s.s.) and A. sculptum. While these species have distinct distribution areas in the country, they are found in sympatry in some transition areas. The current distribution of A. cajennense (s.l.) has important implications to public health, since in Brazil A. sculptum is the most important vector of the bacterium Rickettsia rickettsii, the etiological agent of Brazilian spotted fever.

Control of bovine gastrointestinal nematode parasites using pellets of the nematode-trapping fungus Monacrosporium thaumasium

The viability of a formulation of the fungus Monacrosporium thaumasium associated with ivermectin was evaluated for the biological control of bovine gastrointestinal nematode parasites. Four groups of five calves each were placed in pastures with a stocking rate of 1.6 animal/hectare. In group 1 (control), the calves did not receive any treatment. In group 2, each animal received 20g of pellets of M. thaumasium orally twice a week during a six-month period that began with the onset of the rainy season (October 23, 2000). In group 3, each animal received 20g of pellets of M. thaumasium orally twice a week during the same period as 2, as well as two strategic treatments with ivermectin (200 mcg/kg) on May 10, 2001 and July 5, 2001. In group 4, the animals were treated with ivermectin alone as described for group 3. EPG counts for group 1 were significantly greater (P< 0.01) than those for groups 2 and 3 and the difference at the end of the study period was near 100%. The EPGs of group 4 animals remained high until the first strategic treatment with ivermectin. Values for groups 1 and 4 differed significantly (P< 0.05) from those of groups 2 and 3 from December 2000 onwards. It was concluded that the use of this dose and periodicity of application of M. thaumasium pellets makes the application of anthelminthic treatments unnecessary.

Aplicação de formulação do fungo predador de nematóides Monacrosporium thaumasium (Drechsler, 1937) no controle de nematóides de bovinos

The viability of a formulation of the fungus Monacrosporium thaumasium (Drechsler, 1937) was evaluated for the biological control of bovine gastrointestinal nematode parasites. Two groups of seven female calves each, Holstein ´ Zebu crossbred, four to six months of age, were placed in Cynodon dactilon pastures. In group A, each animal received via oral 20g of pellets of M. thaumasium twice a week during a four-month period that began with the onset of the rainy season (October, 2001). In group B (control), the calves did not receive any treatment. The counts of eggs per gram of faeces (EPG) for animals of the group B were significantly greater (P<0.05) than those for animals from group A and the difference of the EPG between the animals from groups A and B at the end of the experimental period was 88.8%. Cooperia was the most prevalent genus. It is concluded that the use of this dose and the periodicity of application of M. thaumasium pellets were efficient in the control of bovine gastrointestinal nematode parasites.

Controle biológico de tricostrongilídeos (Nematoda: Trichostrongyloidea) gastrintestinais de bovinos pelo fungo Monacrosporium sinense

This study aimed to evaluate the viability of the predatory fungi Monacrosporium sinense (SF 470 isolate) to prey infective trichostrongylids larvae of cattle after the test of passage through the gastrointestinal tract. One hundred grams of pellets with the isolate of M. sinense were orally administered to two six-month-old holstein×zebu crossbred calves. Two similar animals that orally received 100g of pellets without the fungal isolate were used as control. Fecal samples collected at 12, 18, 24, 48, 72 and 96 hours after the treatments were allocated in Petri dishes and in fecal cultures and incubated for 15 days at 25oC. There was significant reduction (P<0.05) of the average number of infective larvae of Cooperia spp. and Haemonchus spp. in the animals treated with the fungus when compared to the control calves. At the end of the experiment, the differences were 69.9% in the Petri dishes and 61.3% in the fecal cultures. The fungi M. sinense was effective in the control of infective gastrointestinal trichostrongylids larvae of cattle in laboratory conditions.

Amblyomma tick species infesting amphibians and reptiles in the seasonally dry Amazon forest, with new host records for Amblyomma rotundatum (Acari: Ixodida: Ixodidae)

Abstract Our study yielded a list of ticks found on amphibians and reptiles at five sites within seasonally dry Amazon forest in Mato Grosso State, central Brazil, in addition to new host records for A. rotundatum. We collected 431 tick specimens: 79 larvae, 115 nymphs, 38 females, and 199 males belonging to A. humerale, A. rotundatum, and Amblyomma sp., on 39 anurans and 21 reptiles. The toads R. guttatus and R. margaritifera and the frog L. pentadactylus are new hosts for A. rotundatum.

Using the fungus Arthrobotrys cladodes var. macroides as a sustainable strategy to reduce numbers of infective larvae of bovine gastrointestinal parasitic nematodes

Research in the area of sanitation in ruminant production has focused on discovery of potential agents for biological control of helminths with nematophagous fungi and has provided evidence of success. The antagonistic potential of the fungus Arthrobotrys cladodes var. macroides on infective larvae of bovine gastrointestinal parasitic nematodes was evaluated by scanning electron microscopy. Additionally, an in vivo test of the resistance to digestive processes and viability of the fungus was carried out using a formulation based on sodium alginate administered orally in cattle. Production of conidia and chlamydospores was high. In in vitro tests, the number of infective nematode larvae was reduced 68.7% by the fungus in the treated group compared to the control group. The interaction between the fungus and the nematodes was confirmed by scanning electron microscopy. Plates containing fecal samples collected after oral administration of 100 g of pellets containing the A. cladodes fungus showed that the fungus survived passage through the gastrointestinal tract of ruminants, grew on agar, formed traps and preyed on L3 larvae of gastrointestinal parasites. The results of the present study provide a new opportunity for alternative, environmentally safe control of ruminant nematodes.