Sheep scab spatial distribution: the roles of transmission pathways.

BACKGROUND: Ovine psoroptic mange (sheep scab) is a highly pathogenic contagious infection caused by the mite Psoroptes ovis. Following 21 years in which scab was eradicated in the UK, it was inadvertently reintroduced in 1972 and, despite the implementation of a range of control methods, its prevalence increased steadily thereafter. Recent reports of resistance to macrocyclic lactone treatments may further exacerbate control problems. A better understanding of the factors that facilitate its transmission are required to allow improved management of this disease. Transmission of infection occurs within and between contiguous sheep farms via infected sheep-to-sheep or sheep-environment contact and through long-distance movements of infected sheep, such as through markets. METHODS: A stochastic metapopulation model was used to investigate the impact of different transmission routes on the spatial pattern of outbreaks. A range of model scenarios were considered following the initial infection of a cluster of highly connected contiguous farms. RESULTS: Scab spreads between clusters of neighbouring contiguous farms after introduction but when long-distance movements are excluded, infection then self-limits spatially at boundaries where farm connectivity is low. Inclusion of long-distance movements is required to generate the national patterns of disease spread observed. CONCLUSIONS: Preventing the movement of scab infested sheep through sales and markets is essential for any national management programme. If effective movement control can be implemented, regional control in geographic areas where farm densities are high would allow more focussed cost-effective scab management.

Molecular characterization and serodiagnostic potential of two serpin proteins in Psoroptes ovis var. cuniculi.

BACKGROUND: Psoroptes ovis var. cuniculi is a common ectoparasite of wild and domestic rabbits worldwide that causes economically devastating losses in commercial rabbit husbandry and significantly affects the overall health of rabbits. Serine proteinase inhibitor (serpin) is present in almost all organisms that are involved in host-pathogen interactions, inflammatory responses, and reproductive development, among others. However, very little research has been carried out on P. ovis var. cuniculi serpins. METHODS: Two serpin genes of P. ovis var. cuniculi (Pso c 27 and PsoSP2 cDNAs) were cloned and molecularly characterized. The transcriptional profiles and tissue localization of these two serpins in P. ovis var. cuniculi were investigated by quantitative real-time PCR and immunohistochemistry, respectively. The potential function of recombinant Pso c 27 and PsoSP2 (rPso c 27 and rPsoSP2) in the serodiagnosis of P. ovis var. cuniculi infestation in rabbits was evaluated using a newly devleoped indirect enzyme-linked immunosorbent assay. RESULTS: Both the 523-residue Pso c 27 and the 240-residue PsoSP2 proteins contained typical serpin domains and signatures. Both Pso c 27and PsoSP2 cDNAs were expressed throughout the life-cycle; specifically, the cDNAs showed significantly higher expression in female mites than in larva, nymph, and male mites (Pso c 27: F(3, 8) = 1935.953, P < 0.0001; PsoSP2: F(3, 8) = 660.669, P < 0.0001). The native Pso c 27 and PsoSP2 proteins localized in the ovary and mouthparts of adult female mites, respectively. Compared to rPsoSP2, rPso c 27 showed better diagnostic efficiency, with higher values of sensitivity, specificity, and area under the receiver operating characteristic curve (rPso c 27 vs rPsoSP2: 96.0 vs 90.0%; 90.91 vs 78.18%; 0.988 vs 0.964, respectively). Moreover, rPso c 27 showed seropositivity in 80% of the rabbits as early as the 2 weeks post-infestation, prior to visible clinical signs and microscopy-positive of skin scrapings. CONCLUSIONS: These results suggest that these two serpins may play essential roles in reproductive development, serum-feeding, and pathogenicity of P. ovis var. cuniculi. Compared to PsoSP2, Pso c 27 appears to be a potential antigen for serodiagnosis of P. ovis var. cuniculi infestation in rabbits, especially at the early stage of infestation.

A single subcutaneous administration of a sustained-release ivermectin suspension eliminates Psoroptes cuniculi infection in a rabbit farm.

BACKGROUND: Psoroptes cuniculi mites are the most common ear parasites infesting breeding female rabbits. The suffering rabbits show cutaneous signs of the infestation in the ears and are prone to secondary infections. OBJECTIVES: This trial was conducted to eliminate P. cuniculi in farm rabbits with a sustained-release ivermectin-loaded solid dispersion suspension (IVM-SD) suspension, and studied the stability of the formulation. ANIMALS: There were 986 breeding female Hyplus rabbits naturally infected with P. cuniculi. METHODS: All rabbits infected with P. cuniculi were subcutaneously administered with a single dose of IVM-SD suspension at 2 mg/kg body weight. Twenty-seven rabbits with severe infections were observed daily and examined on days 0 and 14 to score the lesions and count mites in crusts. RESULTS: Fourteen days after the treatment no live mites were detected, demonstrating 100% therapeutic efficacy. The mean lesion scores decreased from 4.33 to 0.11 in the left ears and from 4.22 to 0.22 in the right ears. No reinfection occurred within 60 days of treatment. CONCLUSIONS: A single subcutaneous administration of the IVM-SD suspension at 2 mg/kg was effective in eliminating P. cuniculi infection in the rabbit farm.

Host transcription factors in the immediate pro-inflammatory response to the parasitic mite Psoroptes ovis.

BACKGROUND: Sheep scab, caused by infestation with the ectoparasitic mite Psoroptes ovis, results in the rapid development of cutaneous inflammation and leads to the crusted skin lesions characteristic of the disease. We described previously the global host transcriptional response to infestation with P. ovis, elucidating elements of the inflammatory processes which lead to the development of a rapid and profound immune response. However, the mechanisms by which this response is instigated remain unclear. To identify novel methods of intervention a better understanding of the early events involved in triggering the immune response is essential. The objective of this study was to gain a clearer understanding of the mechanisms and signaling pathways involved in the instigation of the immediate pro-inflammatory response. RESULTS: Through a combination of transcription factor binding site enrichment and pathway analysis we identified key roles for a number of transcription factors in the instigation of cutaneous inflammation. In particular, defined roles were elucidated for the transcription factors NF-kB and AP-1 in the orchestration of the early pro-inflammatory response, with these factors being implicated in the activation of a suite of inflammatory mediators. CONCLUSIONS: Interrogation of the host temporal response to P. ovis infestation has enabled the further identification of the mechanisms underlying the development of the immediate host pro-inflammatory response. This response involves key regulatory roles for the transcription factors NF-kB and AP-1. Pathway analysis demonstrated that the activation of these transcription factors may be triggered following a host LPS-type response, potentially involving TLR4-signalling and also lead to the intriguing possibility that this could be triggered by a P. ovis allergen.

Localized seborrhoeic dermatitis with hyperhidrosis due to mite infestation in an Iranian cross-breed ram.

A 3-years-old Iranian cross-breed ram with history of repeated local sweating, severe pruritus of body surface was referred to the veterinary clinic. On clinical examination wetness, warmness, pruritus and thickness of affected area were observed. In affected area, hair coat was staring and draggy. Body temperature, heart and respiratory rates were 40.4 degrees C, 120 beat min(-1) and 40 min(-1), respectively. Hematologic indices including packed cell volume, total and differential white blood cell (WBC) and total red blood cell (RBC) were normal. Laboratory examinations of skin scrapings confirmed infestation with Psoroptes ovis. Histopathologic findings included dilation of sweat glands, hyperplasia of sebaceous glands, hyperkeratosis, ulcer and scab formation and eosinophilic dermatitis. History and clinical findings association with the skin scraping and histopathologic findings indicated localized seborrhoeic dermatitis with hyperhidrosis. After treatment with ivermectin at the dose rate of 0.2 mg kg(-1), all clinical signs subsided. This confirmed that the cause of seborrhic dermatitis and hyperhidrosis was mite infestation and other possible causes were ruled out. So this is the first report of localized seborrhoeic dermatitis with hyperhidrosis due to mite infestation in animals.

[Epidemiological investigations of bovine Chorioptes mange in Germany]. / Epidemiologische Erhebungen zur Chorioptes-Räude des Rindes in Deutschland.

Chorioptic mange in cattle has long been recognised as a common external parasitosis in livestock. In order to evaluate the economic importance of Chorioptes bovis-mange, the seasonal prevalence in several types of husbandry in the states of Germany, location of clinical skin symptoms, procedure of diagnosis, influence on milk or meat production, and treatment especially in dairy farming, 1190 German large animal practicioners have been asked by questionnaires from which 367 responded. This paper gives an update on important epidemiological investigations on bovine chorioptic mange due to this inquiry. Since more than one third of the questioned veterinarians see tail mange often, it is of high importance for farm cattle. Chorioptes mange mainly occurs in dairy cattle stocks, and has especially negative effects on milk production and meat productivity. For treatment of this external parasitosis mainly macrocyclic lactons and pyrethroids are used.

Identification of an antigen from the sheep scab mite, Psoroptes ovis, homologous with house dust mite group I allergens.

Infestation of sheep with the ectoparasitic mite Psoroptes ovis, results in a severe allergic dermatitis. Currently, little is known about the allergens/antigens that stimulate the allergic response. We have isolated an 836-bp cDNA from a P. ovis cDNA library which displays strong homology to cysteine proteases and, in particular, to the group I house dust mite allergens Der p 1, Der f 1 and Eur m 1. The cDNA was expressed in Escherchia coli, fused to a hexahistidine tag and the recombinant protein (Pso o 1) purified using a nickel-affinity column. The recombinant Pso o 1 was tested for recognition by immunoglobulin (Ig)G and IgE in serum from P. ovis naïve and P. ovis infested sheep. Using Western blots, both classes of antibody to Pso o 1 were detected in postinfestation serum. In enzyme-linked immunosorbent assays, a pronounced IgG-antibody response to Pso o 1 was detected in five of five sheep 3 weeks postinfestation. The IgE-antibody response to whole mite extract was poor in four of five animals. However, a marked IgE response occurred in the fifth animal, and IgE anti Pso o 1 was detected in the serum.