Improved detection of mixed P. falciparum-P. vivax infection at a rural health centre in Ethiopia using PCR

This study aims to this study is to compare the co-infection Plasmodium falciparum + Plasmodium vivax and compare the detection of cases of mixed-species malaria using light microscopy versus semi-nested multiplex PCR (sPCR). Investigators collected 3060 samples at a rural health centre in Ethiopia from December 2010 to October 2011. Two capillary blood specimens were taken from each patient, one for diagnosis of Plasmodium infection by light microscopy and the other for sPCR-based diagnosis. LM detected 627 positive cases; these samples, together with 582 negatives by LM, were also subjected to sPCR testing. Of the 627 positive samples by LM, 68.4% were positive for P. vivax, 30.5% for P. falciparum, and 1.1% for P. falciparum + P. vivax co-infection. Using the sPCR technique, we identified 788 samples positive for Plasmodium: 33.0% for P. vivax, 26.5% for P. falciparum, 3.7% for P. falciparum + P. vivax co-infection, 2.0% for P. ovale and 0.8% for P. vivax + P. ovale co-infection. In the case of P. falciparum + P. vivax co-infection, light microscopy diagnosis showed a sensitivity of 11.1%, a specificity of 99.8%, a positive predictive value of 71.4% and a negative predictive value of 96.6%. The concordance rate for identifying P. falciparum + P. vivax co-infection (kappa statistic) with microscopy and sPCR was 0.184. The LM approach has low sensitivity for the detection of mixed-species infections, while sPCR is more useful.

Epidemiology, chronobiology and taxonomic updates of Rhinoestrus spp. infestation in horses of Sardinia Isle, Western Mediterranean (Italy)

From January to December 2008, 265 horses slaughtered in Sardinia (Italy) were examined for the presence of Rhinoestrus spp. (Diptera: Oestridae) through the examination of the nasal cavities and pharynges. Larvae were detected in 49% of the horses, with a mean intensity of infestation of 16.09 and abundance of 7.95. A total of 2108 larvae were collected, 66% of which were classified in first instar (L1), 22% in second instar (L2) and 12% in third instar (L3). The most frequent localization of larvae was the ethmoid, while the less one the larynx. According to the dynamics of Rhinoestrus larval stages, three periods in the chronobiology can be considered, the diapause (September-February) characterized by an absolute prevalence of first larval stage; the active phase of the endogenous phase (February-September) with an increase in the percentages of L2 and L3, and the exit phase (May-September), pointed by a further increase of L1. Morphological examination of L3 larvae revealed the presence of the Rhinoestrus purpureus features in 8% of the examined larvae, of 8% of the Rhinoestrus usbekistanicus features, while in 84% of the larvae were evidenced intermediate features. Contrastingly biomolecular analysis of the COI gene of the larvae evidenced uniformity at genetic level, confirming the presence of a unique species in the Mediterranean area. The results of the present paper, reveal the wide diffusion of rhinoestrosis among Sardinian horses, and suggest the need for applying appropriate control measures. Chemotherapy should be very useful if administered during the diapause period, for reducing the presence of L1 stages and interrupting thus the life cycle of this myiasis.

A novel second instar Gasterophilus excretory/secretory antigen-based ELISA for the diagnosis of gasterophilosis in grazing horses

We have developed a novel enzyme-linked immunosorbent assay (ELISA) based on excretory/secretory antigens of second instar Gasterophilus for the diagnosis of gasterophilosis in grazing horses. Between January 2007 and January 2009, two experiments were carried out on free-ranging horses in northwest Spain. During the first year, monthly blood samples were collected from a herd of 25 horses. In the second year, a monthly serological survey was conducted for a total of 398 different horses. All the sera were analyzed by ELISA using excretory/secretory antigens from Gasterophilus intestinalis (GphiL2ES) and Gasterophilus nasalis second-stage larvae (GphnL2ES). Climatic data were collected between January 2007 and January 2009 from local meteorological automated stations to establish the weather pattern in the study area. Observations of Gasterophilus eggs on the horses' hair and third instars passed in the faeces were also done. The kinetics of IgG response decreased against GphiL2ES from January to July, increased slowly from August and rose up to January. After a slight decrease in January, the absorbances against GphnL2ES reduced from April to August, when the lowest values were observed. The IgG values rose until the end of the study in January. Third instars were observed in the faeces in March to May, and Gasterophilus eggs were seen on the horses' hair from June to September. The highest IgG seroprevalences were achieved in winter (January-February; 100%) against both antigens. The lowest percentages of seropositivity were observed in June (3%) to the GphiL2ES, and in July (9%) to the GphnL2ES. The use of antigens from G. intestinalis second-stage larvae was shown to be suitable for diagnosing infestation by G. intestinalis or G. nasalis. We concluded that under oceanic climate conditions, the egg-laying period occurs from late spring, and eggs and first instars are found in the mouth in early summer. During summer the second instars move into the stomach and intestine, where the third-stage larvae remain until the end of winter, when pupation takes place. The adult horse bot fly emerges in the spring. Two treatments for the control of gasterophilosis are suggested: a curative in the summer to eliminate the first instars and a preventive in the autumn to suppress the second instars.