Efficacy of three-week oxytetracycline or rifampin monotherapy compared with a combination regimen against the filarial nematode Onchocerca ochengi.

Onchocerciasis (river blindness), caused by the filarial nematode Onchocerca volvulus, is a major cause of visual impairment and dermatitis in sub-Saharan Africa. As O. volvulus contains an obligatory bacterial symbiont (Wolbachia), it is susceptible to antibiotic chemotherapy, although current regimens are considered too prolonged for community-level control programs.

Analysis of gene expression from the Wolbachia genome of a filarial nematode supports both metabolic and defensive roles within the symbiosis.

The α-proteobacterium Wolbachia is probably the most prevalent, vertically transmitted symbiont on Earth. In contrast with its wide distribution in arthropods, Wolbachia is restricted to one family of animal-parasitic nematodes, the Onchocercidae. This includes filarial pathogens such as Onchocerca volvulus, the cause of human onchocerciasis, or river blindness.

Comparative genomics of the apicomplexan parasites Toxoplasma gondii and Neospora caninum: Coccidia differing in host range and transmission strategy.

Toxoplasma gondii is a zoonotic protozoan parasite which infects nearly one third of the human population and is found in an extraordinary range of vertebrate hosts. Its epidemiology depends heavily on horizontal transmission, especially between rodents and its definitive host, the cat. Neospora caninum is a recently discovered close relative of Toxoplasma, whose definitive host is the dog.

A worm's best friend: recruitment of neutrophils by Wolbachia confounds eosinophil degranulation against the filarial nematode Onchocerca ochengi.

Onchocerca ochengi, a filarial parasite of cattle, represents the closest relative of the human pathogen, Onchocerca volvulus. Both species harbour Wolbachia endosymbionts and are remarkable in that adult female worms remain viable but sessile for many years while surrounded by host cells and antibodies. The basis of the symbiosis between filariae and Wolbachia is thought to be metabolic, although a role for Wolbachia in immune evasion has received little attention.

Onchocerca armillata contains the endosymbiotic bacterium Wolbachia and elicits a limited inflammatory response.

Human onchocerciasis, also known as River Blindness, is a debilitating disease caused by the filarial nematode Onchocerca volvulus. Many, but not all, filarial nematodes carry within their tissues endosymbiotic, Rickettsia-like bacteria of the genus Wolbachia. Onchocerca spp.

Immunisation with a multivalent, subunit vaccine reduces patent infection in a natural bovine model of onchocerciasis during intense field exposure.

Human onchocerciasis, caused by the filarial nematode Onchocerca volvulus, is controlled almost exclusively by the drug ivermectin, which prevents pathology by targeting the microfilariae. However, this reliance on a single control tool has led to interest in vaccination as a potentially complementary strategy. Here, we describe the results of a trial in West Africa to evaluate a multivalent, subunit vaccine for onchocerciasis in the naturally evolved host-parasite relationship of Onchocerca ochengi in cattle.

UMF-078: A modified flubendazole with potent macrofilaricidal activity against Onchocerca ochengi in African cattle.

Background: Human onchocerciasis or river blindness, caused by the filarial nematode Onchocerca volvulus, is currently controlled using the microfilaricidal drug, ivermectin. However, ivermectin does not kill adult O. volvulus, and in areas with less than 65% ivermectin coverage of the population, there is no effect on transmission.

Lack of serologic evidence of Neospora caninum in humans, England.

Retrospective testing of 3,232 serum samples from the general population and 518 serum samples from a high-risk group showed no evidence of human exposure to Neospora caninum in England. Results were obtained by using immunofluorescence antibody testing and ELISA to analyze frequency distribution.

Of mice, cattle, and humans: the immunology and treatment of river blindness.

River blindness is a seriously debilitating disease caused by the filarial parasite Onchocerca volvulus, which infects millions in Africa as well as in South and Central America. Research has been hampered by a lack of good animal models, as the parasite can only develop fully in humans and some primates. This review highlights the development of two animal model systems that have allowed significant advances in recent years and hold promise for the future.

Upregulation of cytokines is detected in the placentas of cattle infected with Neospora caninum and is more marked early in gestation when fetal death is observed.

The protozoan parasite Neospora caninum causes fetal death after experimental infection of pregnant cattle in early gestation, but the fetus survives a similar infection in late gestation. An increase in Th1-type cytokines in the placenta in response to the presence of the parasite has been implicated as a contributory factor to fetal death due to immune-mediated pathological alterations. We measured, using real-time reverse transcription-PCR and enzyme-linked immunosorbent assay, the levels of cytokines in the placentas of cattle experimentally infected with N.

The extent of parasite-associated necrosis in the placenta and foetal tissues of cattle following Neospora caninum infection in early and late gestation correlates with foetal death.

The protozoan parasite Neospora caninum is the most frequently diagnosed abortifacient in the UK and a leading cause of abortion worldwide but the mechanisms leading to abortion are not fully understood. The distribution of parasites and the histopathological changes in the placenta and foetus were compared in 12 cows following experimental infection of cattle with N. caninum in early (n=6) and late (n=6) gestation, by PCR, immunohistology, light microscopy and transmission electron microscopy.

Risk factors for canine neosporosis in farm and kennel dogs in southern Italy.

Neosporosis by Neospora caninum causes losses to livestock production through abortion in cattle while, in dogs, it induces neuromuscolar disease. This study investigated neosporosis seroprevalence associated risk factors (including the seropositivity to leishmaniosis) in dogs of southern Italy, determined the prevalence of N. caninum oocyst shedding and examined the relationship between seroprevalence of neosporosis in farm dogs and cattle.

Lack of resistance after re-exposure of cattle cured of Onchocerca ochengi infection with oxytetracycline.

Although vector control and ivermectin chemotherapy have led to a dramatic reduction in the incidence of river blindness (onchocerciasis), there is a consensus that additional control tools are required to sustain and extend this success. The recognition of endosymbiotic bacteria (Wolbachia) in filariae and their targeting by antibiotics constitutes the most significant and practicable opportunity for a macrofilaricidal therapy in the short-to-medium-term. Using Onchocerca ochengi in cattle, an analog of human onchocerciasis, we have previously shown that oxytetracycline is macrofilaricidal, and protective immunity exists naturally in a subset of animals termed putatively immune.

Eosinophils contribute to killing of adult Onchocerca ochengi within onchocercomata following elimination of Wolbachia.

Many filarial nematodes, including Onchocerca volvulus (the cause of human 'River Blindness'), have a mutually dependent relationship with Wolbachia bacteria. There has been much interest in Wolbachia as a chemotherapeutic target, since there are no macrofilaricidal drugs (i.e.

In a bovine model of onchocerciasis, protective immunity exists naturally, is absent in drug-cured hosts, and is induced by vaccination.

Onchocerciasis (river blindness) is a major parasitic disease of humans in sub-Saharan Africa caused by the microfilarial stage of the nematode Onchocerca volvulus. Using Onchocerca ochengi, a closely related species which infects cattle and is transmitted by the same black fly vector (Simulium damnosum sensu lato) as O. volvulus, we have conducted longitudinal studies after either natural field exposure or experimental infection to determine whether, and under what circumstances, protective immunity exists in onchocerciasis.

Rate of elimination of Wolbachia pipientis by doxycycline in vitro increases following drug withdrawal.

Wolbachia pipientis is an obligate intracellular bacterium within the family Anaplasmataceae that infects many terrestrial arthropods and arthropod-transmitted nematodes (filariae). Several filarial species are major human pathogens, and antibiotics with activity against Wolbachia offer a promising new therapeutic approach, since the adult worms are relatively refractory to conventional anthelmintics but depend on Wolbachia for reproduction and viability. In a natural filarial parasite of cattle, Onchocerca ochengi, intermittent chemotherapy is adulticidal whereas the equivalent dose administered as a continuous treatment is not.

Endogenous and exogenous transplacental infection in Neospora caninum and Toxoplasma gondii.

It is clear from researching the vertical transmission of Neospora caninum in cattle that the terms 'vertical', 'congenital' and, indeed, 'transplacental' are inadequate for describing two extremely different situations that have fundamentally different immunological, epidemiological and control implications. A similar situation pertains to Toxoplasma gondii in different hosts. We advocate the use of the terms 'endogenous transplacental infection (TPI)' to define foetal infection from a recrudescent maternal infection acquired before pregnancy (and probably prenatally) and 'exogenous TPI' to define foetal infection that occurs as a result of an infection of the dam during pregnancy.

Antibiotic chemotherapy of onchocerciasis: in a bovine model, killing of adult parasites requires a sustained depletion of endosymbiotic bacteria (Wolbachia species).

Development of a drug lethal to adult Onchocerca volvulus (i.e., macrofilaricide) is a research priority for the control of human onchocerciasis.

Repeated high doses of avermectins cause prolonged sterilisation, but do not kill, Onchocerca ochengi adult worms in African cattle.

Background: Ivermectin (Mectizan, Merck and CO. Inc.) is being widely used in the control of human onchocerciasis (Onchoverca volvulus) because of its potent effect on microfilariae.

Immunity to Onchocerca spp. in animal hosts.

This review summarizes research using Onchocerca spp. in chimpanzees, cattle and mice to gain insight into the protective immune response to the filarial worm Onchocerca volvulus in humans. In addition, Acanthocheilonema viteae has been evaluated as a surrogate filarial worm for studying immunity to the infection.