Ruta Chalepensis Full Extract and Organic Phases Exhibit Nematocidal Activity Against Haemonchus Contortus Eggs and Infective Larvae (L3).

The ovicidal and larvicidal effect of a full aqueous extract (FE) and two phases: an aqueous (Aq-Ph) and an ethyl acetate (EtOAc-Ph) from Ruta chalepensis (Rc) stems and leaves against Haemonchus contortus (Hc) were assessed. The egg hatching inhibition (EHI) assay and larval mortality (LM) test were performed by triplicate in 96-well micro-titration plates (n=4 wells). The FE against Hc eggs and larvae was assessed at 1.25, 2.5, 5, 10 and 20 mg/mL; and 30, 60, 90, 120,150 and 200 mg/ mL, respectively. The ovicidal effect of Aq-F and EtOAc-F was assessed at 1.25, 2.5, 5, 10 and 20 mg/mL. Plates were incubated at 28 °C for 48 (ovicidal assay) and 72 h (larvicidal assay). The EHI results were considered based on the mean number of eggs hatching failure after 48 h exposure. The LM was recorded after 72 h exposure to the Rc phases and expressed as mortality percentage. The Rc FE caused 96 and 100% EHI at 10 and 20 mg/mL, respectively; meanwhile, 74% LM was recorded at 200 mg/mL (p<0.05). The Aq-Ph showed 78.5% EHI at 2.5 mg/mL. Likewise, the EtOAc-Ph caused 100% EHI in almost all concentrations. Eighteen compounds including alkaloids, cumarins, triterpens, flavonoids, tannins, saponins and sterols were identified by GC-MS analysis. The results indicate that the aqueous extract from Rc possesses bioactive compounds with in vitro nematocidal activity against Hc; mainly in the EtOAc-Ph. Further studies should be performed to elucidate those compounds searching for alternative methods of control of the sheep haemonchosis.

Experimental transmission of Toxocara canis from Blattella germanica and Periplaneta americana cockroaches to a paratenic host.

The present study assessed the capacity of Blattella germanica and Periplaneta americana to disseminate and transmit infective phases of T. canis to rats, which were used as a model paratenic host. P. americana and B. germanica inoculated orally with T. canis larvated eggs shed eggs and larvae in their fecal matter during the first 6days post-inoculation. Larvae were recovered from the brain, lungs, kidneys and liver of rats that had been inoculated with either infected cockroaches or their feces. ELISAs of serum detected an increase of antibodies anti-T. canis excretion-secretion antigens, whereas Western Blot (WB) showed 4 bands (120, 50, 35 and 28kDa) that were similar to those found in positive control rats. Macroscopically, the liver and kidneys of infected rats had hemorrhagic areas with milk-spot-like lesions. The lungs showed diffuse grey protuberances. Histologically, hemorrhagic areas with leucocytic infiltrate were observed in the liver, lungs and kidneys. Some larvae were found within a granuloma that was surrounded by eosinophils and other leucocytic infiltrates. Larvae were found in the brain, but without inflammatory infiltrate. Both cockroach species that ingested larvated eggs of T. canis may shed viable larvae or eggs in their fecal matter. The induction of specific serum antibodies, presence of larvae in tissues and characteristic lesions associated with larval migration in the organs of rats that had ingested either whole adults or feces of B. germanica or P. americana demonstrate the capacity of these cockroaches to transmit toxocariosis to paratenic hosts.

Bollgard cotton and resistance of tobacco budworm (Lepidoptera: Noctuidae) to conventional insecticides in southern Tamaulipas, Mexico.

Insecticide susceptibility in tobacco budworm, Heliothis virescens (F.) (Lepidoptera: Noctuidae), was determined for 8 yr (1991-2001) with larvae sampled from cotton in southern Tamaulipas, Mexico. Before 1996, when Bollgard cotton expressing the Cry1A(c) delta-endotoxin was introduced into the region, two important patterns were documented. The first was economically significant increases in resistance to certain insecticide groups. The second was occurrence of virtually complete control failures in the field during 1994 and 1995. The largest resistance changes were recorded for the type II pyrethroids cypermethrin and deltamethrin. These products are the most widely used products in the region. Resistance ratios for these products increased up to > 100-fold from 1991 to 1995. After 1996, the resistance levels declined. These findings did not occur with other products of scant use (e.g., permethrin, profenofos, and endosulfan) or low tobacco budworm efficacy coupled to a high use pattern (e.g., methyl parathion). This clear trend toward reversal of resistance to type II pyrethroids can be understood, in part, with respect to two factors: 1) the high adoption rate of transgenic cotton in the region, from 31.2% in the beginning (1996) to approximately 90% in 1998; this has considerably curbed the use of synthetic insecticides, with the attending loss of selection pressure on this pest; and 2) the potential immigration to the region of susceptible tobacco budworms from cultivated and wild suitable hosts as well as from transgenic cotton might have influenced the pest population as a whole. The influence of transgenic cotton on southern Tamaulipas can be more clearly seen by the drastic reduction of insecticide use to control this important pest. Now tobacco budworms in this region are susceptible to type II pyrethroids. Two effective and fundamentally different pest management tools are now available to cotton growers in southern Tamaulipas: transgenic cotton, coupled with careful use of pyrethroids, offers the possibility of sustainable and profitable cotton production.

Effects of the synergists piperonyl butoxide and S,S,S-tributyl phosphorotrithioate on propoxur pharmacokinetics in Blattella germanica (Blattodea: Blattellidae).

Effects of the synergists piperonyl butoxide (PBO) and S,S,S-tributyl phosphorotrithioate (DEF) on propoxur pharmacokinetics were examined in the German cockroach, Blattella germanica (L.). Treatment of adult male German cockroaches with the cytochrome P450 monooxygenase inhibitor, PBO, or the esterase inhibitor, DEF, increased propoxur toxicity by 2- and 6.8-fold, respectively, implicating hydrolysis as a major detoxification route of propoxur in the German cockroach. However, significant hydrolytic metabolism could not be demonstrated conclusively in vitro resulting in a conflict between in situ bioassay data and in vitro metabolic studies. In vitro propoxur metabolism with NADPH-fortified microsomes produced at least nine metabolites. Formation of metabolites was NADPH-dependent; no quantifiable metabolism was detected with cytosolic fractions. However, microsomal fractions lacking an NADPH source did produce a low, but detectable, quantity of metabolites (1.6 pmol). PBO inhibited NADPH-dependent propoxur metabolism in a dose-dependent fashion, implicating cytochrome P450 monooxygenases as the enzyme system responsible for the metabolism. Interestingly, DEF also inhibited the NADPH-dependent metabolism of propoxur, albeit to a lower extent. Treatment with PBO or DEF also caused a significant reduction in the cuticular penetration rate of propoxur. The data demonstrate that unanticipated effects are possible with synergists and that caution must be exercised when interpreting synergist results.