Bovine fasciolosis in Tabasco, Mexico

Prevalence of flukes (Fasciola hepatica and paramphistomids) in cattle in south-eastern Mexico

The objective of this study was to determine the risk factors and prevalence of trematodes in south-eastern Mexico. The prevalence of trematodes was determined in 1010 bovines. The study was carried out from October 2018 (n=291) to December 2019 (n=719). Only in 2019 rumen and liver fluke eggs were differentiated. Faecal samples (n=311) were obtained from farms in southeast Mexico located in Tabasco, Chiapas and Campeche. In addition, the presence of flukes in liver and rumen from slaughtered cattle in abattoirs was recorded with a total of 408 samples. A logistic procedure was used to obtain the prevalence and the effect of main risk factors such as land physiography (flooded areas and hills), year, sex, animals' age and type of sample obtained (eggs in faeces and flukes). The general prevalence of flukes in cattle was 32.3 % in 2018 and 41.7 % in 2019. Prevalence of F. hepatica (liver fluke) was 18.6 % (134/719) and that of paramphistomids (rumen fluke) was 33.4 % (240/719). The infected cattle from the slaughterhouse indicated a lower prevalence of F. hepatica (1 %) and rumen fluke (26.7 %) than in farms detected by egg in faeces (41.8 % and 42.1 %, respectively). The physiographic zone was decisive in the presence of F. hepatica and rumen fluke, while sex did not represent a risk factor (P > 0.05). The environmental conditions of the Mexican southeast favour the presence of both liver and rumen fluke.

Genetic diversity and multiplicity of infection in Fasciola gigantica isolates of Pakistani livestock

Fasciola spp. are responsible for over 3 billion US dollars of production loss annually in livestock and cause widespread zoonotic disease. Nevertheless, understating of the emergence and spread of the trematode species is poor. The multiplicity of F. gigantica infection and its spread is potentially influenced by multiple factors, including the abundance of suitable intermediate hosts, climatic conditions favouring the completion of the parasite's lifecycle, and translocation of infected animals, or free-living parasite stages between regions. Here we describe the development of a 'tremabiome' metabarcoding sequencing method to explore the numbers of F. gigantica genotypes per infection and patterns of parasite spread, based on genetic characteristics of the mitochondrial NADH dehydrogenase 1 (mt-ND-1) locus. We collected F. gigantica from three abattoirs in the Punjab and Balochistan provinces of Pakistan, and our results show a high level of genetic diversity in 20 F. gigantica populations derived from small and large ruminants consigned to slaughter in both provinces. This implies that F. gigantica can reproduce in its definitive hosts through meiosis involving cross- and self-breeding, as described in the closely related species, Fasciola hepatica. The genetic diversity between the 20 populations derived from different locations also illustrates the impact of animal movements on gene flow. Our results demonstrate the predominance of single haplotypes, consistent with a single introduction of F. gigantica infection in 85% of the hosts from which the parasite populations were derived. This is consistent with clonal reproduction in the intermediate snail hosts.

Fasciola species and their vertebrate and snail intermediate hosts in East and Southern Africa: a review

A systematic review was conducted focusing on the distribution of Fasciola species and their snail intermediate hosts (IHs) in East and Southern Africa. The reviewed literature showed that both Fasciola hepatica and F. gigantica are present in East and Southern Africa, and infect a wide range of domestic and wild ruminants. Fasciola gigantica was reported in six East African and five Southern African countries, where Radix natalensis (found in low altitudes) was reported to be the main IH. Fasciola hepatica was reported in Tanzania and Ethiopia (East Africa), and in South Africa and Zimbabwe (Southern Africa), where Galba truncatula (found in high altitudes) was documented as the IH in all countries except in Zimbabwe. Both Fasciola species were documented in Tanzania, Ethiopia, Zimbabwe and South Africa. An overlap of the two was observed in areas with an intermediate altitude in Ethiopia and South Africa, where Pseudosuccinea columella was widespread and assumed to transmit both species. Pseudosuccinea columella has been reported in South Africa and Namibia, and proven to transmit F. gigantica in South Africa; its role in Namibia in the transmission of Fasciola species has not been reported. Other lymnaeid species such as R. rubiginosa were reported in South Africa, and R. auricularia in South Africa and Botswana; their role in the transmission of Fasciola species has not been proven. Future studies should aim to determine the role of P. columella in the geographical spread of the two species in East and Southern African countries.

Cross-sectional prevalence of Fasciola gigantica infections in beef cattle in Botswana

A cross-sectional study was carried out to determine the prevalence and distribution of Fasciola gigantica infections in communally grazed and ranch-grazed beef cattle through coprological examination. A total of 8646 cattle (4618 adults, 2843 weaners and 1185 calves) faecal samples were collected during the 24 months of study. Results from this study indicated that only 64 (0.74%; 95% CI 0.57, 0.94%) of the samples were positive for F. gigantica eggs. The positive samples were detected in one (Central) of the six study districts and was restricted to the Tuli Block (commercial) farms in Machaneng village in eastern Botswana. The prevalence of fluke eggs was significantly higher in adult cattle (12.85%; 95% CI 9.72, 16.54%) than weaners (6.49%; 95% CI 3.40, 11.06%) and calves (0.79%; 95% CI 0.02, 4.31%), (χ²(2) = 19.01, p < 0.001). Thus, adults (OR = 18.57; 95% CI 2.54, 135.81%) were approximately 20 times more likely to be infected than calves. By taking liver inspection as a gold standard for diagnosis of fasciolosis, the sensitivity of the sedimentation technique was found to be 72.41% and the specificity 100%, with moderate relationship (κ = 0.53; 95% CI 0.31-0.75) between the two methods. This study has demonstrated that infection of cattle from Botswana, with F. gigantica, was low and distribution of the fluke appeared to be linked to suitable environmental conditions for the intermediate host snail. However, detailed surveillance studies, involving more cattle and areas, are required to verify the true prevalence. Such information would assist in the design of appropriate, strategic and effective fluke control programmes.

The global burden of fasciolosis in domestic animals with an outlook on the contribution of new approaches for diagnosis and control

Fasciolosis is an economically important disease for livestock, as well as being zoonotic. Recent figures on the prevalence of this disease have caused alarm concerning its potential for an increased prevalence in the future. The prevalence of fascioliosis has been documented from different regions of the world, helping us identify areas where future research needs to be focused. This manuscript is a review of the current status of the disease, the pathogenic species involved, diagnostic techniques (with new modifications and comparative specificity, sensitivity, and rapidity of these tests), chemotherapy, and vaccination. This also encompasses inaccurate reports on vaccination and drug development as well as the latest technologies to find promising candidates for drugs and vaccines. Drugs with lower efficacy have been used on some farms which lead to exacerbation of the clinical disease, presumably due to the development of drug resistance. Future studies should be focused on (1) the use of the most reliable diagnostic tests for periodic monitoring of the disease, (2) insights of the ecobiology and transmission dynamics of the snail intermediate host and the best possible methods of their control, (3) in vitro and in vivo testing of chemotherapeutic compounds using sensitive methods, and (4) the identification of novel drug and vaccine candidates using modern molecular markers. This approach may help increase the reliability of chemotherapeutic agents and control nuisance, ultimately reducing the economic losses attributable to the livestock industry around the world.

Bovine fasciolosis: prevalence, effects of treatment on productivity and cost benefit analysis in five districts of Punjab, Pakistan

The present study reports the prevalence, effects of treatment and cost benefit analysis of bovine fasciolosis in five districts of Punjab Province viz Sargodha, Jhang, Muzaffargarh, Lodhran and Layyah. From each of the five districts, 80 animals were selected and fortnightly screened through standard coprological procedures for a period of one year for the presence of eggs of Fasciola species. Of 4800 faecal samples analyzed, 1222 (25.46%) were found positive for fasciolosis. The occurrence of Fasciola (F.) gigantica (22.40%) was higher (P<0.05) than F. hepatica (3.06%). Highest month-wise prevalence (P<0.05) of fasciolosis was found in winter (39.08%) followed in decreasing order by spring (29.50%), autumn (20.33%) and summer (12.92%). District-wise prevalence of fasciolosis was highest (P<0.05) in Sargodha (40.31%) and lowest in Layyah (11.77%) while other districts were having intermediate values of prevalence of fasciolosis. Species-wise prevalence of fasciolosis was found higher (P<0.05) in buffaloes (30.50%) as compared to cattle (20.42%). However, there were no age and sex-related differences (P>0.05) in prevalence of fasciolosis. A strong positive association of grazing (OR=1.81), mixed farming of small and large ruminants (OR=1.39), stagnant pond bathing (OR=2.24) and river/canal bathing (OR=2.06) was found with the prevalence of fasciolosis as compared to stall feeding, separate farming of small and large ruminants and rivers/canal/tap water bathing, respectively. Post-treatment average milk increase of 0.62 L per animal per day with 0.35% higher fat was observed in fasciolicide-treated animals with the cost benefit ratio of 3.9. The results provided significant data on the epidemiology of five districts of Punjab province which may be helpful for the planners and small holder dairy farmers for control of fasciolosis in the study districts.

Monthly changes in body condition scores and internal parasite prevalence in Nguni, Bonsmara and Angus steers raised on sweetveld

The objective of the study was to determine monthly changes in body condition scores, body weights and on the prevalence of internal parasites in Nguni, Bonsmara and Angus steers raised on sweetveld. Body condition scores (BCS), body weights (BW), packed cell volume (PCV) and monthly faecal egg counts (FEC) were determined in 25 Nguni, 15 Bonsmara and 15 Angus steers. Nguni and Bonsmara steers maintained their body condition throughout the study, while the Angus lost condition. The Nguni had the highest PCV levels. The PCV levels tended to decline during the rainy season for all the breeds. The FEC were generally low. Fasciola spp. and strongyle eggs were found in 16.3 and 54.6% of the collected faecal samples, respectively. Of the three breeds, Nguni steers had the lowest parasite infestation levels, with the Bonsmara being more susceptible than the other two breeds. Generally, the egg counts observed throughout the study were low.

Seasonal pattern of bovine fasciolosis in the Kafue and Zambezi catchment areas of Zambia

In order to establish seasonality of bovine fasciolosis in the Southern province of Zambia, 288 cattle were examined at slaughter at Turnpike slaughter slab for 1 year. The examination involved liver inspection and coprological examination. Liver condemnation rates were relatively high at the beginning of both the cold dry season and the rainy season (May/June and December, respectively). All cattle, regardless of age, had higher fluke abundances in the post-rainy season (39.1% young and 42.1% adult) while the lowest rates were in the hot dry season (13.3% young and 14.3% adult). On coprological examination, the highest abundance was in the post-rainy season (45.0%) and the lowest in the cold dry season (24.9%). From November (end of dry season) to February/March (end of rains), more fluke eggs were found than in any other period. The distribution of fluke eggs was significantly different (p<0.001) among the four seasons. Identified associations were: egg counts were highest in post-rainy (mean abundance=146) and lowest in cold dry season (mean abundance=118) at 95% confidence (CI 0.64-1.25). Differences in abundance observed according to origin, sex and age of cattle were not significant on both methods. Based on these results, it may be concluded that Fasciola gigantica was present throughout the year in cattle in Zambia but the abundance was highest in the post-rainy season and lowest in the cold dry season.

Seasonal transmission of Fasciola hepatica in cattle and Lymnaea (Fossaria) humilis snails in central Mexico

A 19-month study on the prevalence of fasciolosis in 30 naturally infected cows, the presence of infected and non-infected Lymnaea (Fossaria) humilis snails, and variation in soil temperature and humidity is reported. The prevalence of fasciolosis in cattle declined from around 50% in March to 30% in July, then, it increased from August, reaching a plateau of 100% in November-January, before gradually declining thereafter. A rise in soil humidity and temperature in June and July, respectively, which peaked between August and November was observed. In July, L. (F.) humilis snails appeared, but the infection could only be found in these in August and November. The number of infected snails did not reflect the infestation rate in cows, even though the infestation kinetics in both hosts behaved as predicted from the life cycle of the parasite.

Seasonal trends of Paramphistomum cervi in Tabasco, Mexico

Thirty rumens were examined every month from May 1989 to April 1992 to establish seasonal trends of infection and their relationship to the climatic factors caused by Paramphistomum cervi in cattle. The cattle were chosen from three municipalities of the Sierra region in Tabasco: Jalapa, Tacotalpa and Teapa. P. cervi was found throughout the year with prevalence between 3.33 and 96.67%, and with a yearly average of 39.10%. The major period of infection was shown in Jalapa. However, the maximum mean intensity was found in Teapa. The prevalence of the infection in all three sites was similar, showing the regional trend of P. cervi infection. Cattle were infected mainly throughout the rainy and windy seasons, during summer, autumn and at the beginning of winter.

Molecular cloning of a member of the Fasciola hepatica saposin-like protein family

A 436-bp complementary DNA (cDNA) was isolated from an adult Fasciola hepatica cDNA expression library by screening with the serum from a rabbit infected with F. hepatica for 4 wk. The deduced amino acid sequence encoded by this cDNA is an 11.5-kDa polypeptide that has significant homology to F. hepatica NK-lysin protein, to several members of saposin-like or NK-lysin protein families, as well as 3 amoebapore precursors of Entamoeba histolytica. The most striking feature observed within this protein, denoted FhSAP-2, is the presence of 6 conserved cysteine residues arranged within 5 amphipathic alpha-helical domains and the presence of 7 hydrophobic residues in strictly conserved positions. Using enzyme-linked immunosorbent assay it was found that rFhSAP-2 is highly reactive with sera from rabbits infected with F. hepatica for 2-14 wk as well as with sera from humans with chronic fascioliasis. An anti-rFhSAP-2 rabbit antiserum reacted with F. hepatica excretory-secretory antigens by Western blot, revealing a major 11.5-kDa and 2 minor 46- and 67-kDa antigenic polypeptides. This suggests that FhSAP-2 may be an antigen released from cytoplasmic storage granules present within F. hepatica parasites. rFhSAP-2 also exhibits a strong lytic activity on human erythrocytes and peripheral blood mononuclear cells. This suggests that cell lysis could be 1 of the biological functions of this protein.

Molecular cloning and expression of Cu/Zn-containing superoxide dismutase from Fasciola hepatica

The cytosolic superoxide dismutase (SOD) of Fasciola hepatica, a causative agent of fascioliasis, was purified and characterized. The enzyme consists of two identical subunits, each with an apparent molecular mass of 17.5 kDa. An analysis of the enzyme's primary structure and inhibition studies revealed that the enzyme is a copper/zinc-containing SOD (Cu/Zn-SOD). The enzyme activity was relatively stable in a broad pH range, from pH 7.0 to 10.0, and the enzyme showed maximum activity at pH 7.5. This enzyme also displayed strong antigenicity against sera of bovine and human subjects with fascioliasis. The SOD gene fragment was amplified by PCR with degenerate oligonucleotide primers derived from amino acid sequences conserved in the Cu/Zn-SODs of other organisms. An F. hepatica cDNA library was screened with the SOD gene fragment as a probe. As a result, a complete gene encoding the Cu/Zn-SOD was identified, and its nucleotide sequence was determined. The gene had an open reading frame of 438 bp and 146 deduced amino acids. Comparison of the deduced amino acid sequence of the enzyme with previously reported Cu/Zn-SOD amino acid sequences revealed considerably high homologies. The coding region of the F. hepatica Cu/Zn-SOD was cloned and expressed in Escherichia coli. Staining of native polyacrylamide gel for SOD activity of the expressed protein revealed SOD activity that was inactivated by potassium cyanide and hydrogen peroxide but not by sodium azide. This means that the presence of the recombinant fusion protein is indicative of Cu/Zn-SOD. The expressed protein also reacted with sera of bovine and human subjects with fascioliasis, but it did not react with sera of uninfected bovine and human subjects.