Sex chromosomes are disproportionately involved in reproductive isolation and adaptation. In support of such a ‘large-X’ effect, genome scans between recently diverged populations or species pairs often identify distinct patterns of divergence on the sex chromosome compared to autosomes. When measures of divergence between populations are higher on the sex chromosome compared to autosomes, such patterns could be interpreted as evidence for faster divergence on the sex chromosome, i.e. ‘faster-X’, or barriers to gene flow on the sex chromosome. However, demographic changes can strongly skew divergence estimates and are not always taken into consideration. We used 224 whole genome sequences representing 36 populations from two Heliconius butterfly clades (H. erato and H. melpomene) to explore patterns of Z chromosome divergence. We show that increased divergence compared to equilibrium expectations can in many cases be explained by demographic change. Among Heliconius erato populations, for instance, population size increase in the ancestral population can explain increased absolute divergence measures on the Z chromosome compared to the autosomes, as a result of increased ancestral Z chromosome genetic diversity. Nonetheless, we do identify increased divergence on the Z chromosome relative to the autosomes in parapatric or sympatric species comparisons that imply post-zygotic reproductive barriers. Using simulations, we show that this is consistent with reduced gene flow on the Z chromosome, perhaps due to greater accumulation of incompatibilities. Our work demonstrates the importance of taking demography into account in order to interpret patterns of divergence on the Z chromosome, but nonetheless provides evidence to support the Z chromosome as a strong barrier to gene flow in incipient Heliconius butterfly species.

Multimodal signals facilitate communication with conspecifics during courtship, but they can also alert eavesdropper predators. Hence, signallers face two pressures: enticing partners to mate and avoiding detection by enemies. Undefended organisms with limited escape abilities are expected to minimize predator recognition over mate attraction by limiting or modifying their signalling. Alternatively, organisms with anti-predator mechanisms such as aposematism (i.e. unprofitability signalled by warning cues) might elaborate mating signals as a consequence of reduced predation. We hypothesize that calls diversified in association with aposematism. To test this, we assembled a large acoustic signal database for a diurnal lineage of aposematic and cryptic/non-defended taxa, the poison frogs. First, we showed that aposematic and non-aposematic species share similar extinction rates, and aposematic lineages diversify more and rarely revert to the nonaposematic phenotype. We then characterized mating calls based on morphological (spectral), behavioural/physiological (temporal) and environmental traits. Of these, only spectral and temporal features were associated with aposematism. We propose that with the evolution of antipredator defences, reduced predation facilitated the diversification of vocal signals, which then became elaborated or showy via sexual selection.

Changes in concentrations of IgM and IgG antibodies to Brucella were monitored for at least 13 mo by an enzyme-linked immunosorbent assay (ELISA) in 52 patients with culture-positive brucellosis. Two main patterns were observed. After an initial peak, 29 patients (56%) had a steady drop in their IgG levels, whereas 23 (44%) had more than one peak over time. All patients with a chronic form of brucellosis or a relapse were in the second group. In most cases, Brucella antibodies, although falling to low levels, remained measurable. Cutoff levels for IgM and IgG were calculated after considering serum antibody concentrations in people who had recovered from an infection. A separate normal range was established for occupationally exposed workers. On admission, sera from all patients contained Brucella antibody levels greater than established cutoff levels. Our results show that ELISA is an excellent method for diagnosis and follow-up of brucellosis.

The rise of imported malaria cases and the high fatality rate in Europe make the search for new and easy diagnostic methods necessary. Rapid diagnosis tests (RDTs) are, in part, developed to cover the lack of diagnosis experience. Unfortunately, our data suggest that the accuracy of RDTs is insufficient and could increase the number of incorrect malaria diagnoses.In recent years, countries in which malaria is not endemic have reported high and increasing numbers of imported malaria cases, with fatalities up from 3.8 to 20% (2). Preventing fatal outcomes in malaria cases requires early recognition of infection, accurate laboratory diagnosis, and prompt therapy (2). Unfortunately, health-care personnel in countries where malaria is not endemic frequently lack experience in the microscopic diagnosis of malaria. In Italy, 80% of cases had less than a 1-week elapse between the onset of malaria symptoms and the microscopic diagnosis, but the average diagnosis took 8.5 days and the range was 1 to 28 days (3). This fact makes the search for new and easy diagnostic methods necessary. Rapid diagnosis tests (RDTs) for malaria might offer a valid alternative to microscopy (5).We studied 206 pre-and posttreatment samples from 169 patients in 1998 and 1999 by microscopic diagnosis and seminested multiplex PCR (4). These samples were also tested using three commercial RDT kits; 189 samples from 149 patients were tested with the ParaSight-F Kit (Becton Dickinson), 197 samples from 126 patients were tested with the OptiMal Kit (Flow Incorporated), and 54 samples from 41 patients were tested with the ICT Pf/Pv kit (Amrad). All patients (with ages of 16 months to 72 years) presented a history of fever and travel in the previous year to an area of malaria endemicity.RDTs were performed according to the manufacturers' instructions. All microscopy-positive samples were confirmed by PCR (4). Furthermore, PCR detected 6 samples with mixed infections (4 Plasmodium falciparum plus P. malariae and 2 P. falciparum plus P. ovale) from samples that were characterized as P. falciparum-only by microscopy and 24 more positive samples (12 P. falciparum, 4 P. ovale, 6 P. malariae, and 2 P. vivax). The three RDT methods showed a high rate of false positives and false negatives (Table 1). Moreover, 29.2% of positive non-P. falciparum samples rendered a positive P. falciparum result when the ParaSight-F test was used, which suggests a high number of cross-reactions, as this test according to the manufacturer detects only P. falciparum infections. In the same way, according to the manufacturers, the OptiMal and ICT Pf/Pv kits are able to detect P. falciparum specifically and the other Plasmodium spp. unspecifically. Our data, however, show that e Average time in which a sample is still positive by RDT (negative by microscopy and PCR) after treatment.

Sexually transmitted disease (STD) remains a major public health challenge in developed countries, exacerbated by the advent of the HIV epidemic. The objectives of this study were to assess the prevalence of serological markers of syphilis, HIV-1/2, HTLV-I/II, HBV, and HCV infections among immigrant sex workers in Madrid, Spain and to characterize the HIV-1 variants in seropositive individuals. Sera from 762 immigrant commercial sex workers (75.3% from sub-Saharan Africa, 18.2% from South America, and 6.4% from Eastern Europe) were collected between 1998 and 2003 in Madrid and examined. Antibody detection was performed by screening assays (RPR, ELISAs) and confirmed by FTA-Abs, LIAs and Western-blot tests. HIV-1 subtyping was carried out by phylogenetic analyses of the protease and envelope genes. Antibodies to HIV-1 were found in 5.2%, while 3.5% tested positive for HBsAg, 3% for syphilis antibodies, 0.8% for HCV antibodies, and 0.2% for HTLV-I antibodies. None were reactive for HIV-2 or HTLV-II antibodies. HIV-1 seroprevalence among Africans and Ecuadorians was 4.5 and 10.9%, respectively. All HIV-1 seropositive Ecuadorians were transsexual men, and 28.6% had active syphilis infection. Up to 80% of HIV-1 positive specimens were characterized as non-B subtypes, with subtypes G, A, and G/A recombinants being the most frequent among African individuals. In contrast, South Americans with HIV-1 infection carried exclusively subtype B variants. A relatively high proportion of immigrant sex workers in Madrid were infected with HIV-1 and syphilis, whereas infections with hepatitis viruses or HTLV were uncommon.