The animal reservoir of Tunga penetrans in severely affected communities of north-east Brazil

Tungiasis is a zoonotic ectoparasitosis caused by the sand flea Tunga penetrans L. (Siphonaptera: Tungidae). This disease is hyperendemic in poor communities of north-east Brazil, causing considerable morbidity in affected human populations, but the animal reservoirs have not been investigated previously in Brazil. To assess the prevalence and intensity of T. penetrans infection in domestic and peri-domestic animals, as well as in the human population, we surveyed two typical communities of north-east Brazil: an urban slum and a traditional fishing village. In the slum we examined 849 humans, 121 cats, 82 dogs, 2 pigs, 2 rabbits, 1 monkey and 56 rodents, comprising 34 rats (Rattus rattus L.) and 22 mice (Mus domesticus L). In the fishing village we examined 505 humans, 68 dogs, 37 cats, 7 donkeys, 4 cattle, 3 pigs and 1 monkey. Tungiasis was common among dogs and cats of both communities, with respective prevalence rates of 67.1% (95% CI: 55.8-77.1) and 30.9% (95% CI: 20.2-43.3) in dogs, 49.6% (95% CI: 40.4-58.8) and 32.4% (95% CI: 18.0-49.8) in cats. Slum rats were 41.2% (95% CI: 24.6-59.3) infested, but the other animals were not. Human prevalence rates were 54.4% (95% CI: 51.0-57.8) in the slum and 52.1% (95% CI: 47.6-56.5) in the fishing village. High prevalence rates (range 31-67%) of tungiasis in humans, pets and rats (but apparently not other animals) indicate the need for an eco-epidemiological approach to control of this anthropo-zoonotic problem.     

Effects of Monoclonal Antibodies,Cationized Ferritin,and Other Organic Molecules on Adhesion of Pasteuria penetrans Endospores to Meloidogyne incognita

The incidence of adhesion of Pasteuria penetrans endospores to Meloidogyne incognita second-stage juveniles (J2) was studied after pretreatment of the latter with monoclonal antibodies (MAb), cationized ferritin, and other organic molecules in replicated trials. Monoclonal antibodies developed to a cuticular epitope of M. incognita second-stage juveniles gave significant reductions in attachment of P. penetrans endospores to treated nematodes. MAb bound to the entire length of J2 except for the area of the lateral field, where binding was restricted to the incisures. Since reductions in attachment with MAb treatment were modest, it is uncertain if these results implicated a specific surface protein as a factor that interacted in binding of the endospore to the nematode cuticle. Endospore attachment was decreased following treatment of the nematode with the detergents sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB). Endospore attachment to live nematodes was significantly greater than attachment to dead nematodes. Attachment rates of three P. penetrans isolates to M. incognita race 3 varied between isolates. The effects of neuraminidase, pronase, pepsin, trypsin, lipase, and Na periodate on endospore attachment were inconsistent. The cationic dye alcian blue, which binds sulfate and carboxyl groups on acidic glycans, had no consistent effect on endospore attachment. The incidence of endospore attachment was significantly lower but modest, at best, for nematodes that were treated with cationized ferritin alone or cationized ferritin following monoclonal antibody. The lack of consistency or extreme reduction in most experiments suggests that attachment of P. penetrans spores to M. incognita is not specified by only one physico-chemical factor, but may involve a combination of at least two physico-chemical factors (including surface charge and movement of the J2). This points to a need for analysis of combined or factorial treatment effects.     

Antibodies from Chicken Eggs as Probes for Antigens from Pasteuria penetrans Endospores

The bacteria Pasteuria spp. have been identified as among the most promising of several microbial organisms currently under investigation as biological control agents of plant-parasitic nematodes. As part of our goal to develop methods to discriminate isolates of Pasteuria penetrans with different host preferences, we investigated the potential of developing antibody probes to identify endospores of different isolates of P. penetrans. Polyclonal IgY antibodies were raised in chickens against endospores of P. penetrans isolates P20 and P100. Hens were injected with P20 or P100 endospore suspensions and boosted at 14 days. Anti-spore titers were determined with ELISA on yolk extracts of individual eggs as a function of time. The highest titers were found in eggs produced at 22 to 35 days after initial injections. Yolk extracts showing the highest titers were combined and processed to provide partially purified IgY preparations. SDS-PAGE and immunoblot analyses identified protein antigens with Mr values of 23-24, 46, and 57-59 KDa common to both P20 and P100 endospores. One protein antigen with an Mr value of 62 KDa was unique to the PI00 endospores. The IgY antibodies reduced the attachment of Pasteuria endospores to their nematode hosts, indicating antibody interaction with antigens on the endospore surface that are involved in the recognition and attachment processes.     

穿透支原体LAMPs诱导NF-kB激活介导小鼠巨噬细胞凋亡

研究穿透支原体(Mpe)脂质相关膜蛋白(LAMPs)能否诱导小鼠巨噬细胞凋亡,并阐明其可能的分子机制,以了解Mpe潜在的致病性.用Annexin-V-FITC凋亡检测试剂盒和DNA Ladder方法检测Mpe LAMPs诱导体外培养的小鼠巨噬细胞系Raw264.7细胞的凋亡.以间接免疫荧光和Western blotting方法检测经Mpe LAMPs处理的小鼠巨噬细胞NF-κB的激活和NF-kB抑制剂吡咯啉烷二甲基硫脲(PDTC)对细胞凋亡的影响.结果表明:Mpe LAMPs能诱导小鼠巨噬细胞发生早期或晚期凋亡;Mpe LAMPs能诱导激活小鼠巨噬细胞的NF-κB,使其从细胞浆中转位到细胞核内;PDTC能显著地抑制经处理的小鼠巨噬细胞的NF-κB的激活,且能抑制Mpe LAMPs诱导的巨噬细胞发生凋亡.因此,Mpe LAMPs诱导小鼠巨噬细胞凋亡可能与NF-kB的激活有关,因而Mpe可能是一个重要的致病因素.     

Collateral damage: rapid exposure-induced evolution of pesticide resistance leads to increased susceptibility to parasites

Although natural populations may evolve resistance to anthropogenic stressors such as pollutants, this evolved resistance may carry costs. Using an experimental evolution approach, we exposed different Daphnia magna populations in outdoor containers to the carbamate pesticide carbaryl and control conditions, and assessed the resulting populations for both their resistance to carbaryl as well as their susceptibility to infection by the widespread bacterial microparasite Pasteuria ramosa. Our results show that carbaryl selection led to rapid evolution of carbaryl resistance with seemingly no cost when assessed in a benign environment. However, carbaryl-resistant populations were more susceptible to parasite infection than control populations. Exposure to both stressors reveals a synergistic effect on sterilization rate by P. ramosa, but this synergism did not evolve under pesticide selection. Assessing costs of rapid adaptive evolution to anthropogenic stress in a semi-natural context may be crucial to avoid too optimistic predictions for the fitness of the evolving populations.     

Techniques for image analysis of movement of juveniles of root-knot nematodes encumbered with Pasteuria penetrans spores

Root-knot nematodes (Meloidogyne spp.) are the most significant plant-parasitic nematodes that damage many crops all over the world. The free-living second stage juvenile (J2) is the infective stage that enters plants. The J2s move in the soil water films to reach the root zone. The bacterium Pasteuria penetrans is an obligate parasite of root-knot nematodes, is cosmopolitan, frequently encountered in many climates and environmental conditions and is considered promising for the control of Meloidogyne spp. The infection potential of P. penetrans to nematodes is well studied but not the attachment effects on the movement of root-knot nematode juveniles, image analysis techniques were used to characterize movement of individual juveniles with or without P. penetrans spores attached to their cuticles. Methods include the study of nematode locomotion based on (a) the centroid body point, (b) shape analysis and (c) image stack analysis. All methods proved that individual J2s without P. penetrans spores attached have a sinusoidal forward movement compared with those encumbered with spores. From these separate analytical studies of encumbered and unencumbered nematodes, it was possible to demonstrate how the presence of P. penetrans spores on a nematode body disrupted the normal movement of the nematode.     

The effects of multiple infections on the expression and evolution of virulence in a Daphnia-endoparasite system

Multiple infections of a host by different strains of the same microparasite are common in nature. Although numerous models have been developed in an attempt to predict the evolutionary effects of intrahost competition, tests of the assumptions of these models are rare and the outcome is diverse. In the present study we examined the outcome of mixed-isolate infections in individual hosts, using a single clone of the waterflea Daphnia magna and three isolates of its semelparous endoparasite Pasteuria ramosa . We exposed individual Daphnia to single- and mixed-isolate infection treatments, both simultaneously and sequentially. Virulence was assessed by monitoring host mortality and fecundity, and parasite spore production was used as a measure of parasite fitness. Consistent with most assumptions, in multiply infected hosts we found that the virulence of mixed infections resembled that of the more virulent competitor, both in simultaneous multiple infections and in sequential multiple infections in which the virulent isolate was first to infect. The more virulent competitor also produced the vast majority of transmission stages. Only when the less virulent isolate was first to infect, the intrahost contest resembled scramble competition, whereby both isolates suffered by producing fewer transmission stages. Surprisingly, mixed-isolate infections resulted in lower fecundity-costs for the hosts, suggesting that parasite competition comes with an advantage for the host relative to single infections. Finally, spore production correlated positively with time-to-host-death. Thus, early-killing of more competitive isolates produces less transmission stages than less virulent, inferior isolates. Our results are consistent with the idea that less virulent parasite lines may be replaced by more virulent strains under conditions with high rates of multiple infections.     

Oxidized Positions of Fatty Acyl Moieties of Phosphatidyl-ethanolamine in Liposome Autoxidation

Liposomes of soybean and egg yolk phosphatidylethanolamine (PE) were oxidized in the presence of copper. Fatty acyl moieties with hydroxy and hydroperoxy groups attached were converted to methyl esters. The methyl esters were separated in TLC and then separated on silicic acid thin layer plates containing AgNO₃. After GLC purification, hydrogenated and trimethylsily- lated samples were analyzed for positional isomers in MS. Fatty acids, 18:2 and 18:3 in soybean PE and 18:2, 20:4, and 22:6 in egg yolk PE were examined. A singlet oxygen mechanism was presumably involved in part, but to explain the whole isomer pattern, some yet unexplained mechanism appears to be involved.     

Characterization of 2,4-D Binding to the Auxin-binding Protein Purified from Etiolated Mung Bean Seedlings

New acetylenic nematicidal compound, penipratynolene (1), methy (2′R)-4-(2′-hydroxy-3′-butynoxy)benzoate, together with two known compounds, 6-methoxycarbonylpicolinic acid (2) and 2,6-pyridinedicarboxylic acid (3), were isolated from the culture filtrate of Penicillium bilaiae Chalabuda. The structures of 1–3 were established by spectroscopic methods. The absolute configuration of 1 was confirmed by using a modified version of Mosher’s method. Compounds 1–3 showed nematicidal activity of 77%, 52%, and 98%, respectively, by a bioassay at 300 mg/l with the root-lesion nematode Pratylenchus penetrans.