Fitness cost in field and laboratory Aedes aegypti populations associated with resistance to the insecticide temephos.

BACKGROUND: The continued use of chemical insecticides in the context of the National Program of Dengue Control in Brazil has generated a high selective pressure on the natural populations of Aedes aegypti, leading to their resistance to these compounds in the field. Fitness costs have been described as adaptive consequences of resistance. This study evaluated the biological and reproductive performance of A. aegypti strains and a field population resistant to temephos, the main larvicide used for controlling mosquitoes. METHODS: Comparative tests were performed with a resistant field population from the municipality of Arcoverde, Pernambuco State, Brazil, with a high rate of temephos resistance (RR = 226.6) and three isogenetic laboratory strains from the same origin (Araripina municipality, Pernambuco): RecR (RR = 283.6); RecRNEx (RR = 250.5), a strain under a process of resistance reversion; and RecRev (RR = 2.32), a reversed susceptible strain used as an experimental control. RESULTS: Our study revealed that the absence of selective pressure imposed by exposure to temephos, for five consecutive generations, led to a discrete reduction of the resistance ratio and the response of the detoxifying enzymes. Most of the 19 biological parameters were impaired in the resistant strains and field population. The analysis of the fertility life table confirmed the presence of reproductive disadvantages for the resistant individuals. Similarly, the longevity, body size, and total energetic resources were also lower for the resistant females, except for the last two parameters in the field females (Arcoverde). In contrast, the sex ratio and embryonic viability suffered no interference in all strains or population evaluated, regardless of their status of resistance to temephos. CONCLUSIONS: The reproductive potential and survival of the resistant individuals were compromised. The parameters most affected were the larval development time, fecundity, net reproduction rate, and the generational doubling time. These fitness costs in the natural population and laboratory strains investigated are likely associated with maintaining the metabolic mechanism of resistance to temephos. Our results show that despite these costs, the highly temephos resistant populations can compensate for these losses and successfully overcome the control actions that are based on the use of chemical insecticides.

Splenectomy Improves Hemostatic and Liver Functions in Hepatosplenic Schistosomiasis Mansoni.

BACKGROUND: Schistosomiasis mansoni is a chronic liver disease, in which some patients (5-10%) progress to the most severe form, hepatosplenic schistosomiasis. This form is associated with portal hypertension and splenomegaly, and often episodes of gastrointestinal bleeding, even with liver function preserved. Splenectomy is a validated procedure to reduce portal hypertension following digestive bleeding. Here, we evaluate beneficial effects of splenectomy on blood coagulation factors and liver function tests in hepatosplenic schistosomiasis mansoni compared to non-operated patients. METHODOLOGY/PRINCIPAL FINDINGS: Forty-five patients who had undergone splenectomy surgery were assessed by laboratory analyses and ultrasound examination and compared to a non-operated group (n = 55). Blood samples were obtained for liver function tests, platelet count and prothrombin time. Coagulation factors (II, VII, VIII, IX and X), protein C and antithrombin IIa, plasminogen activator inhibitor-1 were measured by routine photometric, chromogenic or enzyme-linked immunosorbent assays, while hyperfibrinolysis was defined by plasminogen activator inhibitor-1 levels. Both groups had similar age, gender and pattern of periportal fibrosis. Splenectomized patients showed significant reductions in portal vein diameter, alkaline phosphatase and bilirubin levels compared to non-operated patients, while for coagulation factors there were significant improvement in prothrombin, partial thromboplastin times and higher levels of factor VII, VIII, IX, X, protein C and plasminogen activator inhibitor-1. CONCLUSION/SIGNIFICANCE: This study shows that the decrease of flow pressure in portal circulation after splenectomy restores the capacity of hepatocyte synthesis, especially on the factor VII and protein C levels, and these findings suggest that portal hypertension in patients with hepatosplenic schistosomiasis influences liver functioning and the blood coagulation status.

Human plasma lipid modulation in schistosomiasis mansoni depends on apolipoprotein E polymorphism.

BACKGROUND: Schistosomiasis mansoni is a parasitic liver disease, which causes several metabolic disturbances. Here, we evaluate the influence of Apolipoprotein E (APOE) gene polymorphism, a known modulator of lipid metabolism, on plasma lipid levels in patients with hepatosplenic schistosomiasis. METHODOLOGY/PRINCIPAL FINDINGS: Blood samples were used for APOE genotyping and to measure total cholesterol (TC), LDL-C, HDL-C and triglycerides. Schistosomiasis patients had reduced TC, LDL-C and triglycerides (25%, 38% and 32% lower, respectively; P<0.0001) compared to control individuals, whereas HDL-C was increased (10% higher; P = 0.0136). Frequency of the common alleles, ε2, ε3 and ε4, was similar (P = 0.3568) between controls (n = 108) and patients (n = 84), implying that APOE genotype did not affect susceptibility to the advanced stage of schistosomiasis. Nevertheless, while patient TC and LDL-C levels were significantly reduced for each allele (except TC in ε2 patients), changes in HDL-C and triglycerides were noted only for the less common ε2 and ε4 alleles. The most striking finding, however, was that accepted regulation of plasma lipid levels by APOE genotype was disrupted by schistosomiasis. Thus, while ε2 controls had higher TC and LDL-C than ε3 carriers, these parameters were lower in ε2 versus ε3 patients. Similarly, the inverse relationship of TG levels in controls (ε2>ε3>ε4) was absent in patients (ε2 or ε4>ε3), and the increase in HDL-C of ε2 or ε4 patients compared to ε3 patients was not seen in the control groups. CONCLUSION/SIGNIFICANCE: We confirm that human schistosomiasis causes dyslipidemia and report for the first time that certain changes in plasma lipid and lipoprotein levels depend on APOE gene polymorphism. Importantly, we also concluded that S. mansoni disrupts the expected regulation of plasma lipids by the different ApoE isoforms. This finding suggests ways to identify new metabolic pathways affected by schistosomiasis and also potential molecular targets to treat associated morbidities.

Relationship between splenomegaly and hematologic findings in patients with hepatosplenic schistosomiasis.

BACKGROUND: Schistosomiasis is a tropical disease. Patients who develop hepatosplenic schistosomiasis have clinical findings including periportal fibrosis, portal hypertension, cytopenia, splenomegaly and gastrointestinal hemorrhage. OBJECTIVE: The aim of this study was to analyze the hemostatic and hematologic findings of patients with schistosomiasis and correlate these to the size of the spleen. METHODS: Fifty-five adults with hepatosplenic schistosomiasis and 30 healthy subjects were selected through a history of contact with contaminated water, physical examination and ultrasound characteristics such as periportal fibrosis and splenomegaly in the Gastroenterology Service of the Universidade Federal de Pernambuco. Blood samples were collected to determine liver function, blood counts, prothrombin (international normalized ratio), partial thromboplastin time and fibrinogen and D-Dimer levels using the Pentra 120 hematological analyzer (HORIBA/ABX), Density Plus (test photo-optical Trinity Biotech, Ireland) and COBAS analyzer 6000 (Roche). Furthermore, the longitudinal size of the spleen was measured by ultrasound (Acuson X analyzer 150, Siemens). The Student t-test, the Fisher test and Pearson's correlation were used to analyze the results with statistical significance being set for a p-value < 0.05. RESULTS: The mean age was higher for the Study Group than for the Control Group (54 ± 13.9 vs. 38 ± 12.7 years). The average longitudinal diameter of the spleen was 16.9 cm (Range: 12.3-26.3 cm). Anemia is a common finding in patients with schistosomiasis (36.3%). The mean platelet and leukocyte counts of patients were lower than for the Control Group (p-value < 0.001). Moreover, the international normalized ratio (1.42 vs. 1.04), partial thromboplastin time (37.9 vs. 30.5 seconds) and D-Dimer concentration (393 vs. 86.5 ng/mL) were higher for the Study Group compared to the Control Group. CONCLUSION: This study suggests that hematological and hemostatic abnormalities are associated with splenomegaly, hypersplenism and portal hypertension.