Genetic relationships between sheep, cattle and human Echinococcus infection in Tunisia

Allozyme variation at seven polymorphic loci (GPI, EST, MDH, MPI, DIA, PEP, PGM) was studied to examine genetic variation within and between sheep, cattle and human populations of Echinococcus granulosus in Tunisia. A high degree of genetic similarity was shown between the cysts of the three host origins. Nevertheless, whereas, the ovine and human samples were highly similar, the cattle samples were slightly different genetically. We conclude that humans are mostly infected by parasites originating from sheep liver. The intense deficiency in heterozygotes was partly artefactual (Wahlund effect) and partly due to self-fertilisation.     

Occurence of sclerotinia stem rot of fenugreek caused by <Emphasis Type="Italic">Sclerotinia trifoliorum</Emphasis> and <Emphasis Type="Italic">S. sclerotiorum</Emphasis> in Tunisia

Fenugreek is an annual leguminous crop grown for hay and grains in Tunisia. It is also considered a valuable rotation crop with cereals. Sclerotinia rot was observed in production fields since 2010. The survey conducted in 2013 revealed that the incidence of diseased plants varied between 5 and 20%. The identification of isolates of Sclerotinia obtained from fenugreek plants with symptoms of stem rot was determined using morphological and molecular criteria. The size, shape and abundance of sclerotia in potato dextrose agar (PDA) cultures were used to classify isolates as S. sclerotiorum or S. trifoliorum. A comparison of colony diameter on PDA after 24, 48 and 72 h at 25 °C, showed that one isolate grew faster (36 mm/day) than the other 10 isolates (14.8 mm/day). There was a significant difference in sclerotial size between the fast and the slow growing isolates, but there was no significant difference in the number of sclerotia produced after 3 weeks on PDA. Two of the slow growing isolates exhibited ascospore dimorphism, whereas the fast growing isolate did not. PCR amplification with the primer pair ITS5/ITS4 produced a fragment of 560 base pairs from the fast growing isolate and 1000 base pairs from all of the slow growing isolates. The ITS sequences of the fast growing isolate had 100% homology with S. sclerotiorum, whereas those of the slow growing isolates had 100% homology with S. trifoliorum. Isolates of both species were pathogenic on fenugreek seedlings in the greenhouse assay and there was no significant difference in the percentage of dead plants two weeks after inoculation between the two species.     

Recent sedimentation rates in Garaet El Ichkeul Lake, NW Tunisia, as affected by the construction of dams and a regulatory sluice

Purpose

Ichkeul National Park, NW Tunisia, is a UNESCO Biosphere Reserve. Garaet El Ichkeul Lake is known for its seasonal variability in water level and salinity. In recent decades, the waterbody has been affected by the construction of new hydraulic structures. To reduce the impacts of dams and to maintain the sustainability of the ecosystem, a sluice was built at the outlet of the lake, and it operated for the first time in 1996. This paper describes an investigation of recent sedimentation dynamics in Ichkeul Lake, determined by radiometric dating of sediment cores.

Materials and methods

A sediment core was collected with a UWITEC gravity corer at the deepest, central part of the lake in August 2009. Specific activities of unsupported lead-210 (²¹⁰Pb) and caesium-137 (¹³⁷Cs) were measured in the core, enabling calculation of recent sediment accumulation rates (SAR). Published radiometric data from nearby sediment cores, collected in 1997 and 1982, provide a comparison.

Results and discussion

The measured excess ²¹⁰Pb inventory was 5300?±?500?Bq?m^?2, leading to an estimation of constant flux of 165?±?16?Bq?m^?2?yr^?1, a value higher than the best estimate for local atmospheric fluxes (123?±?12?Bq?m^?2?yr^?1) and the flux estimated from the core collected in 1982 (48?Bq?m^?2?yr^?1). The ¹³⁷Cs inventory was 3550?±?120?Bq?m^?2, two times higher than the historical ¹³⁷Cs atmospheric deposition in the area. The ¹³⁷Cs profile displayed a distinct peak, but the ¹³⁷Cs depth-distribution did not follow the pattern expected from atmospheric deposition. Application of the constant rate of supply (CRS) model, with the reference point method, produced a chronology and SAR values comparable to those found in previous work. The whole ¹³⁷Cs profile was quantitatively reconstructed from the historical records of atmospheric deposition, using the system-time-averaged (STA) model.

Conclusions

The CRS and STA models provide consistent sediment accumulation results for the whole data set, considering the time resolution of the chronology (~6?years) and analytical uncertainties. Results from cores sampled in 1982, 1997 and 2009 reveal an increasing SAR trend, from ~0.25?g?cm^?2?yr^?1 in the early 1940s to ~0.67?g?cm^?2?yr^?1 at present. In the 13?years since installation of sluice gates at Tinja, SAR in the central Ichkeul Lake has not declined. Thus, if siltation continues at the present rate, shallowing of the lake will seriously affect the hydromorphology and ecology of this important lake.     

Cystic Hydatic Disease in Sheep: Treatment with Percutaneous Aspiration and Injection with Dipeptide Methyl Ester

An in vitro and in vivo study was conducted to show the effect of dipeptide methyl ester on the protoscolices of Echinococcus granulosus and in naturally infected sheep. Easily punctured cysts were located by ultrasonography. A PAIR and PAI method were performed bythe injection of dipeptide methyl ester into these cysts at a final concentration of 110 mmol/L. Follow-up was conducted monthly by ultrasonography. After injection of the compound, the sheep were sacrificed at different times from 6 to 17 weeks. The size and the morphological aspect of treated cysts were noted. Samples were collected for histologyand electron microscopy. In conclusion, these studies revealed significant and rapid detachment of the membrane of the treated cyst and alteration of the inner membrane in less than 5 min after injection of the drug, confirming the effect of the compound on the laminated layer of the parasite.     

Vaccination of calves with an attenuated cell line of Theileria annulata and the sporozoite antigen SPAG-1 produces a synergistic effect

The sporozoite surface antigen, SPAG-1 and the attenuated schizont infected Tunisian line CL1 of Theileria annulata have been shown, in previous studies, to induce variable levels of protection against homologous and heterologous sporozoite challenge, respectively. We report here the result of a vaccination trial comparing the protection level induced by the SPAG-1 antigen (as a recombinant full length His tagged protein) and the attenuated cell line, used singly or in combination. The results, after challenge of immunised calves with a lethal dose of sporozoites, show that SPAG-1 provides limited protection (one out of seven calves surviving), while the attenuated cell line provides moderate protection (three out of seven calves recovered). The combination of SPAG-1 and the attenuated cell line induced the best protection as indicated by the survival of all the vaccinated calves. These results, together with a range of parasitological and clinical parameters, demonstrate the enhanced protection provided by combining sporozoite and schizont antigens in vaccination against tropical theileriosis.     

Ultrasonographic screening for cystic echinococcosis in sheep in Tunisia

Sheep from the areas of Fondouk-Jeddid, Bir Mchergua and El Fahs, located in the Northeast of Tunisia, were examined by ultrasonography between 2001 and 2004 in order to assess their infection with Echinococcus granulosus, the agent of hydatid disease, and to evaluate this method as an efficient aire for hydatid cysts. A total of 1039 sheep, aged between 1 and 14 years was examined. The highest prevalence was found in sheep aged more than 8 years. The least infected animals were aged between 1 and 2 years. All hydatid cysts detected by ultrasound were located in the liver. In all age-groups, the dead cysts were more numerous than viable cysts. Eighteen positive sheep were autopsied and a comparison between ultrasound and autopsy results was performed. The results showed a prevalence of about 40% for the three areas. Ultrasonography allowed the cysts, deep or superficial to localize in the central or left part in relation to the caudal vena cava of the animals. Consequently, all the cysts were not detected with this technique. This work shows that ultrasonography confirms the importance of ovine hydatid cyst in Tunisia and that its use as a mass screening approach for cystic echinococcosis in sheep could be helpful for the monitoring of this disease in a hydatid control program without great stress for the animals.     

Genetic structure of Verticillium dahliae isolates infecting olive trees in Tunisia using AFLP,pathogenicity and PCR markers

Since 2006, verticillium wilt of olive induced by Verticillium dahliae has caused considerable economic losses in olive orchards in Tunisia. The genetic structure of V. dahliae isolates collected from different olive growing regions was investigated using virulence tests, vegetative compatibility grouping (VCG) and amplified fragment length polymorphism (AFLP) analyses. In total, 42 isolates of V. dahliae from diseased olive trees were tested. Cluster analysis and principal coordinate analysis revealed that geographic origin was the main factor determining the genetic structure of V. dahliae populations and both methods indicated a genetic separation between the central and coastal isolates. Isolates were divided into two major groups: the AFLP‐I group included all isolates from Sidi Bouzid, Kairouan, Kasserine and Sfax (centre of the country) and the AFLP‐II group included isolates from Monastir, Zaghouane, Sousse, Mahdia (coastal region), and two isolates from Sfax. Analysis of the molecular variance (amova ) indicated a significant level of genetic differentiation among (76%) and within (23%) the two populations. Analyses of both the defoliating (D) and non‐defoliating (ND) pathotypes and VCG markers indicated that most of the isolates belong to VCG 2A and 4B/ND pathotype. The disease severity was highly variable among the isolates tested (P < 0·05) with no evidence of association between aggressiveness and geographical origin of the isolates. Overall, results of this study revealed a clear association between the genetic diversity of the isolates and their geographic origin, but not between genetic diversity and virulence patterns.     

Infection of calves with Theileria annulata in Tunisia: Economic analysis and evaluation of the potential benefit of vaccination

A field study aiming to estimate the costs of tropical theileriosis was carried out in an endemic region of the North of Tunisia. Three farms were monitored for two successive summer seasons. A total number of 56 calves and 12 sentinel cows were monitored. Calves were ranked into four groups: non infected animals, diseased animals with clinical tropical theileriosis, sub-clinical Theileria annulata infected animals with anaemia and sub-clinical T. annulata infected animals without anaemia. The total costs due to disease and infection were estimated to be 15,115.058 TD (Euro 9388.20). A high proportion of these costs (50.81%) is accounted for by asymptomatic infection. Sub-clinical infections with anaemia showed the highest losses in live weight, while disease cases (prevalence 42.86%) are responsible for 23.64% of the losses with death as the most important element. A cost-benefit analysis of vaccination using a Tunisian attenuated cell line vaccine was also undertaken. Considering that the vaccine would cost 5 TD (Euro 3.10), the cost-benefit ratio of vaccination is 23.7. Sensitivity analysis of the vaccination costs shows that the indifference decision point is around 118 TD (Euro 73.29).     

SOIL LIMING AND MINERAL FERTILIZATION FOR ROOT NODULATION AND GROWTH OF FABA BEANS IN AN ACID SOIL IN TUNISIA

Faba beans (Vicia faba L) are grown in northern Tunisia where annual rainfall approaches 1200 mm and where the soil acidity is the most limiting factor for plant growth. Aluminum (Al) and manganese (Mn) toxicities provide a hostile environment to root growth. To alleviate such a problem, farmers use selected acid-tolerant species. However, crop yields remain far below their optimal levels. Liming, a practice to eliminate acidity, has never been tried in this area before. This research aimed to evaluate the impact of lime and mineral fertilizers on root nodulation, plant uptake and yield of faba beans using a pot experiment. Treatments were combinations of two rates of calcium carbonate with three rates of superphosphate and three rates of potassium sulfate. Liming produced significantly higher number and weight of nodules on roots as well as higher nitrogen, phosphorus, and potassium contents in plant tissue. Liming also increased shoot growth and bean yield.     

Exogenous application of calcium silicate improves salt tolerance in two contrasting tomato (Solanum lycopersicum) cultivars

The aim of this study was to investigate the impact of application of calcium silicate and salinity singly, on plant growth and nutritional behavior and photosynthetic pigments of tomato. Application of sodium chloride (NaCl) induced significant reduction in plant development and growth parameters. Salt stress also led to an accumulation of sodium (Na⁺) and a decrease in potassium (K⁺) concentration. Reduction of chlorophyll and carotenoid in leaves were amongst other symptoms in salt-affected plants in 2 cultivars. Rio Grande was qualified as salt sensitive and Moneymaker as the salt tolerant genotype. Application of Silicon (Si) only improved plant behaviour as compared to control. Furthermore, Si induced ameliorative effects on the growth potential of NaCl stressed plants. This Si-ameliorative effect on plant varied depending on the considered cultivar and Si concentration. Based on these results, application of calcium silicate was suggested as an alternative way to ameliorate the harmful effects of salinity on tomato.