SOME PAST AND ONGOING PROJECTS: FIELD INVESTIGATIONS
Molecular detection of Rickettsia africae in ticks from Cameroon
AndreaÂ Vanegas,ChristianÂ Keller,Â Andreas Krueger,Â Ralf MatthiasÂ Hagen,Â HagenÂ Frickmann,
Alexandra Veit, Bernhard Fleischer, Manchang Tanyi, Mbunkah Daniel Achukwi*, Sven Poppert.
*TOZARD PO Box 59 Bambili-Bamenda Cameroon
Tick-borne rickettsioses are emerging zoonotic infections in many African countries.Â R.Â africaeÂ isÂ theÂ mostÂ frequentÂ rickettsiaÂ speciesÂ withÂ humanÂ pathogenicÂ potentialÂ inÂ Africa.Â It belongs to the group of spotted fever group rickettsiae and transmission is caused by Amblyomma ticks. Human pathogens of the order Rickettsiales have been detected in blood samples of patients withÂ acuteÂ febrileÂ illnessÂ andÂ ticksÂ samplesÂ inÂ theÂ SouthÂ ofÂ Cameroon.Â SerologicalÂ studiesÂ carried outÂ inÂ humansÂ fromÂ differentÂ areasÂ in CameroonÂ haveÂ demonstratedÃÂ previousÂ infectionsÂ with Rickettsia spp.. However, the geographical distribution and the prevalence of R. africae in their tick vectors from the North region of Cameroon are unknown.
Materials and Methods
Tick samples were collected from cattle in the central slaughterhouse in Ngaoundere Adamawa region, Cameroon.Â 47,1%Â ofÂ adultÂ ticksÂ wereÂ identifiedÃÂ asÂ Amblyomma variegatum,Â whichÂ isÂ aÂ knownÂ vectorÂ thatÂ canÂ transmitÂ rickettsiaeÂ toÂ humansÂ onÂ theÂ African continent.RiphicephalusÂ spp.,Â HyalommaÂ spp. and BoophilusÂ spp.Â were alsoÂ identified.Â The presence of rickettsial DNA was investigated in Ambylomma variegatum ticks using both real-time and conventional PCR assays for the rickettsial ompB gene.
Results and Discussion:Â
FromÂ 149Â AmblyommaÂ variegatumÂ ticksÂ tested,Â 85Â (57 %)Â wereÂ positiveÂ forÂ rickettsial DNA.Â OmpBÂ sequencingÂ showedÂ aÂ highÂ degreeÂ ofÂ conservationÂ and homologyÂ withÂ deposited sequences of R. africae, which were previously detected in ticks from other regions of Cameroon. R.Â africaeÂ areÂ presentedÂ inÂ AmbylommaÂ ticksÂ fromÂ theÂ Adamawa, Cameroon. Ambylomma variegatum is a potential vector of spotted fevers in Cameroon. R. africae should be considered by physicians in patients with febrile illness and typical skin rashes.
Cattle ticks in Cameroon: is Rhipicephalus (Boophilus) microplus absent in Cameroon and the Central African region? Ticks Tick Borne Dis. 2015 Mar;6(2):117-22. doi: 10.1016/j.ttbdis.2014.10.005. Epub 2015 Jan 7
- 1IRAD, Bambui, PO Box 51, Bamenda, Cameroon. (Now at TOZARD PO Box 59 Bambili-Bamenda Cameroon.
- 2CIRDES, UnitÃÂ© de Recherche sur les Bases Biologiques de la lutte IntÃÂ©grÃÂ©e (URBIO), 01 BP 454 Bobo-Dioulasso 01, Burkina Faso.
In most parts of the world, ticks are rapidly developing resistance to commonly used acaricides thus rendering control difficult. This constraint is further compounded by the introduction of new species in areas where they did not exist before. Such is the case with the introduction into and rapid spread of Rhipicephalus (Boophilus) microplus in some countries of West Africa. With the looming threat of its further spread in the region, the objective of the present study was to update knowledge on cattle ticks in Cameroon.
Results and Discussions: Among 19,189 ticks collected monthly from 60 animals in 5 herds from March 2012 to February 2013, Rh. (B.) decoloratus was the most abundant species with a relative prevalence of 62.2%, followed by Amblyomma variegatum (28.4%), Rh. (B.) annulatus (0.2%), Rh. (B.) geigyi (0.03%), other Rhipicephalus spp. (8.4%) and Hyalomma spp. (0.3%). Rh. (B.) decoloratus and A. variegatum were also the most widely distributed in space. Infestation rate was generally high, with average tick count/animal of about 80 during peak periods. Tick distribution and abundance in the different sites was as varied as the underlying factors, among which the most important were management systems and climatic factors. The effects of rainfall and temperature were confounded by other factors and difficult to evaluate. However, it appears tick development depends among other factors, on a humidity threshold, above which there is not much more effect. Rh. microplus was not found during this study, but more extensive tick collections have to be done to confirm this. In conclusion, cattle tick infestation in Cameroon remains an important cause for concern. Farmers need assistance in the use and management of acaricides in order to increase their efficiency and reduce the development of resistance. Although Rh. microplus was not found, its introduction from other West African countries is imminent if adequate measures, especially in the control and limitation of animal movements, are not taken. Rh. Microplus has been reported in Ivory Coast, Burkina Faso, Benin etc.
Achukwi Mbunkah Daniel,1, 2* Harnett William,2 Enyong Peter3 & Renz Alfons4. Successful vaccination against Onchocerca ochengi infestation in cattle using live Onchocerca volvulus infective larvae. Parasite Immunology, 2007, 29, 113 ÃÂ116 DOI: 10.1111/j.1365-3024.2006.00917.x
1Institute of Agricultural Research for Development, Wakwa Regional Centre, P. O. Box 65 Ngaoundere, Cameroon.
2Strathclyde University, Department of Immunology, 31 Taylor street, Glasgow, G4 ONR,ÃÂ ÃÂ U.K
ÃÂ 3Medical Research Centre (IMPM) Kumba, Cameroon.
ÃÂ 4University of TÃÂ¼bingen, Tierphysiologisches Institut, Auf der Morgenstelle 28, 72076 ÃÂ¼bingen, Germany.
Abstract: Epidemiological evidence has led to the hypothesis that the concurrent and predominant transmission of Onchocerca ochengi by Simulium damnosum s.l. in sub-saharan Africa could lead to the protection of humans against onchocerciasis caused by Onchocerca volvulus (zooprophylaxis). To gain support for this hypothesis, we investigated whether exposure to O. volvulus could protect cattle from O. ochengi. Gudali calves were vaccinated with live O. volvulus infective larvae and subsequently challenged with O. ochengi infective larvae whilst raised in a fly-proof house. Post-challenge adult parasite and microfilaria development, IgG1 and lgG2 subclass antibodies response to Ov10/Ov11 recombinant Onchocerca antigens and peripheral blood lymphocyte proliferative responses to O. ochengi crude antigens were studied over a one-year period. The vaccinated-challenged animals had 83 to 87% less adult O. ochengi parasites than non-vaccinated-challenged animals. IgG1 and lgG2 antibodies to Ov10/Ov11 recombinant Onchocerca antigens were invoked by non-vaccinated-challenged animals but not by most (80%) of the vaccinated-challenged animals. These findings support the idea of cross protection (zooprophylaxis) due to inoculation of humans with O. ochengi infective larvae under natural transmission conditions in endemic areas.ÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂ Key words: Vaccination, Cattle, Onchocerca ochengi, Onchocerca volvulus, infective larvae, Lymphocytes, IgG subclass antibodies, Recombinant O. volvulus antigens.
Eberle R, Brattig N, Trusch M, Schlter H, Achukwi MD, Eisenbarth A, Renz A, Liebau E, Perbandt M, Betzel C.ÃÂ Isolation, identification and functional profile of excretory-secretory peptides from Onchocerca ochengi.ÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂ Acta Trop. 2014 Dec 3. pii: S0001-706X(14)00384-2. doi: 10.1016/j.actatropica.2014.11.015.
Abstract: Parasitic helminthes excrete or secrete a variety of functional molecules into the internal milieu of their mammalian hosts and arthropod vectors which reveal distinct immunomodulatory and other biological activities. We identified and initially characterized the low molecular weight peptide composition of the secretome from the filarial parasite Onchocerca ochengi. A total of 85 peptides were purified by liquid chromatography and further characterized by mass spectrometry. 72 of these peptides were derived from already described Onchocerca proteins and 13 peptide sequences are included in the sequence of uncharacterized proteins. Three peptides, similar to host defense peptides, revealed antibacterial activity. The present analysis confirms the putative involvement of low molecular weight compounds in the parasite-host cross-talk.ÃÂÃÂ Copyright ÃÂ© 2014. Published by Elsevier B.V. KEYWORDS: Antibacterial activity; Excretory ÃÂsecretory products; Filaria; Functional peptides; Onchocerca