Amblyomma cajennense (Acari: Ixodidae) tick populations susceptible or resistant to acaricides in the Mexican Tropics.

The objectives of the present study were: (i) to identify the frequency of cattle farms with a cohabitation of Amblyomma cajennense and Rhipicephalus microplus, (ii) to determine the status of susceptibility or resistance to acaricides used in Veracruz, Mexico, on A. cajennense populations and (iii) to identify factors associated with A. cajennense resistant to acaricides. Fifty farms were visited to determine the presence of ticks (A. cajennense and R. microplus) and to collect engorged A. cajennense individuals. From these, 24 A. cajennense populations were evaluated in resistance bioassays using discriminating doses of acaricides. The acaricides tested were organophosphates (chlorpiriphos, coumaphos and diazinon), pyrethroids (flumethrin, deltamethrin and cypermethrin), amidines (amitraz) and fipronil (a broad spectrum N-phenylpyrazole insecticide). A. cajennense infesting bovines were identified in 86% (43/50) of the farms visited, and 100% of the farms sampled (43/43) had cohabitation between R. microplus and A. cajennense. Of the farm owners or managers surveyed, 87.5% could not distinguish the morphological difference between tick genera. Populations of A. cajennense were 100%, 91.7% and 12.5% resistant to diazinon, coumaphos and chlorpyriphos (organophosphates), respectively, and 12.5% to amitraz, as were those susceptible to flumethrin and fipronil. In conclusions, populations of A. cajennense showed a high frequency of resistance to the organophosphates tested and to amitraz. Factors associated with the resistance to acaricides in A. cajennense were not identified.

Natural occurrence of lethal aspergillosis in the cattle tick Rhipicephalus (Boophilus) microplus (Acari:Ixodidae).

The purpose of this study was to describe an unreported entomopathogenic fungus that naturally infects the cattle tick Rhipicephalus (Boophilus) microplus (Acari: Ixodidae). Engorged female ticks, showed symptoms of fungal infection after controlled tick infestation of cattle. Infected ticks developed a distinctive dark colour, a pale mould grew over the cuticle and the ticks eventually died covered with fungal conidiophores. The responsible fungus was isolated and cultured on mycological medium and submitted to microscopic morphology, biochemical phenotyping and 18S rRNA ribotyping analyses, which identified it as aflatoxin-producing Aspergillus flavus. Spores from the cultured fungus were experimentally sprayed over healthy engorged female ticks, obtaining an 80% prevalence of experimental infection of healthy ticks and their egg masses, the larval progeny after incubation under laboratory conditions was also infected. These results demonstrate that A. flavus is the causative agent of the natural fungal disease of the cattle tick R. microplus described here.

Megaselia scalaris reared on Rhipicephalus (Boophilus) microplus laboratory cultures.

Different laboratory cultures of the acarine tick Rhipicephalus (Boophilus) microplus (Canestrini, 1888) (Ixodida: Ixodidae) were infested by small Megaselia scalaris (Loew, 1866) (Diptera: Phoridae) flies. Larvae of this species exhibited opportunistic parasitism predominantly on engorged female ticks, causing severe damage to their cuticle through which the flies were able to reach R. microplus internal organs, on which they fed until developing into pupae in the tick's remains. The flies were kept by continuous propagation on fresh ticks over six generations during which the same parasitoid behaviour was observed. Here we report on an ixodid tick laboratory culture used for rearing M. scalaris.

[Purulent meningitis. Presentation of 47 cases]. / Meningitis purulenta. Presentación de 47 casos.

We report 47 patients with purulent meningitis who were seen at our institution during the last 3 years. In 42.5% of patients an upper respiratory infection previous to the onset of the clinical features of meningitis was demonstrated. We had positive bacteriological results in 47% of cases. In the remaining patients the culture was negative. 56% of these had received previous antibiotic therapy. Only 4 patients died, all of them with initial septic shock. The therapy of choice was i.v. ampicillin, at a dose of 1-3 g/4 hours.

Intracerebral calcifications in childhood lymphoblastic leukemia. A new iatrogenic disease?

A 3-year-old child diagnosed as having acute lymphatic leukemia (ALL), developed meningeal leukemia 36 months after the onset of the disease. He was twice subjected to cranial irradiation plus intrathecal methotrexate (i.t. MTX). Skull radiology showed bilateral gyriform calcification of both cerebral hemispheres. Hematological relapse was first detected 5 years after diagnosis and the child died 5 months later. The most striking findings of a right frontal lobe biopsy and the postmortem examination were wide calcium deposits located in the cortex and in the adjacent white matter. Intense demyelination as well as areas of neuron poverty were apparent in the necropsy but in the biopsy specimen. The possible interrelationship between such deposition and cranial irradiation and/or i.t. MTX suggests a new iatrogenic disorder.