In-vivo therapeutic efficacy trial with artemisinin derivative, buparvaquone and imidocarb dipropionate against Babesia equi infection in donkeys

Comparative efficacy of buparvaquone and imidocarb in inhibiting the in vitro growth of Babesia bovis

Introduction

B. bovis is an apicomplexan parasite responsible for bovine babesiosis, a tick-borne disease with a worldwide impact. The disease remains inefficiently controlled, and few effective drugs, including imidocarb dipropionate (ID), are currently available in endemic areas. The objective of this study was to evaluate whether buparvaquone (BPQ), a drug currently used to treat cattle infected with the Babesia-related Theileria spp. parasites, could be active against Babesia parasites. Herein, we compared the effect of ID and BPQ on B. bovis growth in vitro erythrocyte culture.

Methods

We compared the effect of ID and BPQ on the culture-adapted Texas T2Bo strain of B. bovis. In vitro cultured parasites were incubated with ID and BPQ at two starting parasitemia levels (PPE), 0.2% and 1%. In vitro cultured parasites were treated with ID or BPQ at concentrations ranging from 10 to 300 nM, during 4 consecutive days. Parasitemia levels were daily evaluated using microscopic examination. Data was compared using the independent Student's t-test.

Results and discussion

Both ID and BPQ significantly inhibited (p < 0.05) the growth of B. bovis, regardless of the initial parasitemia used. At 1% parasitemia, BPQ had lower calculated inhibitory concentration 50 (IC50: 50.01) values than ID (IC50: 117.3). No parasites were found in wells with 0.2% starting parasitemia, treated previously with 50 nM of BPQ or ID, after 2 days of culture without drugs. At 1% parasitemia, no parasite survival was detected at 150 nM of BPQ or 300 nM of ID, suggesting that both drugs acted as babesiacidals.

Conclusion

Overall, the data suggests that BPQ is effective against B. bovis and shows a residual effect that seems superior to ID, which is currently the first-line drug for treating bovine babesiosis globally.

Artemisinin derivatives induce oxidative stress leading to DNA damage and caspase-mediated apoptosis in Theileria annulata-transformed cells

BACKGROUND

Bovine theileriosis caused by the eukaryotic parasite Theileria annulata is an economically important tick-borne disease. If it is not treated promptly, this lymphoproliferative disease has a significant fatality rate. Buparvaquone (BPQ) is the only chemotherapy-based treatment available right now. However, with the emergence of BPQ resistance on the rise and no backup therapy available, it is critical to identify imperative drugs and new targets against Theileria parasites.

METHODS

Artemisinin and its derivatives artesunate (ARS), artemether (ARM), or dihydroartemisinin (DHART) are the primary defence line against malaria parasites. This study has analysed artemisinin and its derivatives for their anti-Theilerial activity and mechanism of action.

RESULTS

ARS and DHART showed potent activity against the Theileria-infected cells. BPQ in combination with ARS or DHART showed a synergistic effect. The compounds act specifically on the parasitised cells and have minimal cytotoxicity against the uninfected host cells. Treatment with ARS or DHART induces ROS-mediated oxidative DNA damage leading to cell death. Further blocking intracellular ROS by its scavengers antagonised the anti-parasitic activity of the compounds. Increased ROS production induces oxidative stress and DNA damage causing p53 activation followed by caspase-dependent apoptosis in the Theileria-infected cells.

CONCLUSIONS

Our findings give unique insights into the previously unknown molecular pathways underpinning the anti-Theilerial action of artemisinin derivatives, which may aid in formulating new therapies against this deadly parasite. Video abstract.

Low seroprevalence of equine piroplasmosis in horses exported from the Netherlands between 2015 and 2021

Equine piroplasmosis (EP) is a tick-borne disease affecting horses, donkeys, mules and zebras, caused by the intracellular apicomplexan protozoa Babesia caballi and Theileria equi. The geographical distribution of EP is closely related to the distribution of its vector tick species belonging to the genera of Dermacentor, Rhipicephalus and Hyalomma. Since the discovery of Dermacentor reticulatus ticks in 2007 and the first reported autochthonous cases in the South of the Netherlands in 2012, no data on the (sero)prevalence of EP in horses in the Netherlands have been reported and it remains unclear whether B. caballi and T. equi have been able to establish themselves in the Netherlands. This study aims to give an update on the current status of EP in horses in the Netherlands using data from serological tests performed in the context of export and screening of 12,881 horses from 2015 through 2020. Horses were categorized as “Dutch,” “Foreign,” or “Unknown” based on microchip number. The overall seroprevalence of EP in Dutch horses was found to be 0.5% (95% exact CI [0.4–0.7]), compared to 1.9% (95% exact CI [1.3–2.6]) in horses in the category “Foreign” and 1.7% (95% exact CI [1.2–2.3]) in horses in the category “Unknown.” In addition, the seroprevalence per country in the category “Foreign” ranged from 0% (0.95% exact CI [0–2.8]) for Ireland to 6.0% (0.95% exact CI [3.5–9.3]) for Spain. In light of the reports on the seroprevalence during the outbreak of autochthonous EP reported in 2012 and on seroprevalences of EP in other countries in Northwestern Europe, the seroprevalence of EP in horses exported from the Netherlands is very low. However, the higher seroprevalence of EP in horses from abroad warrants the need for the monitoring of EP, as tick vectors are present in the Netherlands and the import of horses from endemic areas increases the chances of EP becoming more prevalent in the Netherlands.

Evaluation of the inhibitory efficacy of quaternary ammonium compounds on in vitro growth of Theileria equi parasite in MASP culture

Equine piroplasmosis has become a global problem of the equine husbandry sector. Haemoprotozoans evolved very quickly and developed resistance against most of the current available drugs. Phospholipid membrane synthesis by choline kinase enzyme is vital for propagation of intra-erythrocytic protozoa parasites. This pathway was targeted in the present study. Quaternary ammonium salts (QAS) and their analogues act against choline and hamper the biosynthesis process for phosphatidylcholine. We analysed anti-T. equi activity of three QAS - decamethonium bromide (DMB), decyl trimethyl ammonium bromide (DTAB) and dodecyl trimethyl ammonium bromide (DDTAB). Theileria equi parasites in vitro treated with different concentrations of DMB, DDTAB and DTAB. Drug treated T. equi failed to multiply further in the viability test. The IC₅₀ value of DMB, DDTAB and DTAB for growth inhibition of T. equi was 14.0 μM, 469.51 nM and 558.40 nM, respectively. DMB, DDTAB and DTAB treated T. equi parasites were observed to be devoid of internal structures, showing pyknotic and degenerative appearances. Various concentration of DMB, DDTAB and DTAB were analysed for their cytotoxicity and haemolytic activity on horse's PBMCs and RBCs. DMB was less than 10% cytotoxic to PBMCs, while DDTAB and DTAB were 40%-50% cytotoxic at 1000 μM concentrations. The respective CC₅₀ values were 7202.96 μM, 1026.26 μM and 1263.95 μM. DMB and DTAB showed least haemolytic activity (<3%); whereas DDTAB was more haemolytic to RBCs at highest concentration of 2000 μM. The respective CC₅₀ values of these drugs were 224495.3 μM, and 39101.35 μM; 713.54 μM. Specific selective index for DMB, DDTAB and DTAB values with respect to host's PBMC and RBC cells, were 514.50, 2185.81, 2263.52 and 16035.38, 1519.75, 70023.91, respectively. These data indicated its non-toxicity to host's cells and selective potential of anti-T. equi in vitro activity.

Botanical Medicines Cryptolepis sanguinolenta, Artemisia annua, Scutellaria baicalensis, Polygonum cuspidatum, and Alchornea cordifolia Demonstrate Inhibitory Activity Against Babesia duncani

Human babesiosis is a CDC reportable disease in the United States and is recognized as an emerging health risk in multiple parts of the world. The current treatment for human babesiosis is suboptimal due to treatment failures and unwanted side effects. Although Babesia duncani was first described almost 30 years ago, further research is needed to elucidate its pathogenesis and clarify optimal treatment regimens. Here, we screened a panel of herbal medicines and identified Cryptolepis sanguinolenta, Artemisia annua, Scutellaria baicalensis, Alchornea cordifolia, and Polygonum cuspidatum to have good in vitro inhibitory activity against B. duncani in the hamster erythrocyte model. Furthermore, we found their potential bioactive compounds, cryptolepine, artemisinin, artesunate, artemether, and baicalein, to have good activity against B. duncani, with IC₅₀ values of 3.4 μM, 14 μM, 7.4 μM, 7.8 μM, and 12 μM, respectively, which are comparable or lower than that of the currently used drugs quinine (10 μM) and clindamycin (37 μM). B. duncani treated with cryptolepine and quinine at their respective 1×, 2×, 4× and 8× IC₅₀ values, and by artemether at 8× IC₅₀ for three days could not regrow in subculture. Additionally, Cryptolepis sanguinolenta 90% ethanol extract also exhibited no regrowth after 6 days of subculture at doses of 2×, 4×, and 8× IC₅₀ values. Our results indicate that some botanical medicines and their active constituents have potent activity against B. duncani in vitro and may be further explored for more effective treatment of babesiosis.

Anti-piroplasmic activity of novobiocin as heat shock protein 90 inhibitor against in vitro cultured Theileria equi and Babesia caballi parasites

Theileria equi and Babesia caballi are the causative agents of equine piroplasmosis (EP). Currently, imidocarb dipropionate (ID) is the only available drug for treating the clinical form of EP. Serious side effects and incomplete clearance of infection is a major drawback of ID. Heat-shock proteins (Hsp) play a vital role in the life cycle of these haemoprotozoans by preventing alteration in protein conformation. These Hsp are activated during transmission of EP sporozoites from the tick vector (poikilotherm) to the natural host (homeotherm) and facilitate parasite survival. In the present study, we targeted the heat shock protein 90 (Hsp-90) pathway of T. equi and B. caballi by using its inhibitor drug - novobiocin. Dose-dependent efficacy of novobiocin on the growth of T. equi and B. caballi was observed in in vitro culture. Additionally, we examined dose-dependent cell cytotoxicity on host peripheral mononuclear cells (PBMCs) and haemolytic activity on equine red blood cells (RBC). In vivo organ toxicity of novobiocin was also assessed in a mouse model. The IC₅₀ (50 % inhibitory concentration) value of novobiocin against T. equi and B. caballi was 165 μM and 84.85 μM, respectively. Novobiocin significantly arrested the in vitro growth of T. equi and B. caballi parasites at 100 μM and 200 μM drug concentration, respectively. In vitro treated parasites had distorted nuclear material and showed no further viability. Based on the equine PBMCs and RBC, the drug was found to be safe even at 1000 μM concentration and the CC₅₀ (50 % cytotoxicity concentration) values were 11.63 mM and 261.97 mM. Very high specific selective index (SSI) values (70.47 and 1587) were observed for equine PBMCs and RBC, respectively. Organ-specific biochemical markers and histopathological examination indicated no adverse effect of the drug at a dose rate of 50 mg kg body weight in the mouse model. The results demonstrate the growth inhibitory effect of novobiocin against T. equi and B. caballi parasites and its safety for host cell lines with very high SSI. Hence, it can be inferred that the Theileria/Babesia Hsp-90 family are potential drug targets worthy of further investigation.

Protein Kinase Inhibitors Arrested the In-Vitro Growth of Theileria equi

INTRODUCTION

Theileria equi is an intra-erythrocytic apicomplexean protozoa that infect equines. Protein kinases (PK), key molecules of the apicomplexean life cycle, have been implicated as significant drug targets. The growth inhibitory efficacy of PK inhibitors against Theileria/Babesia animal parasites have not been documented so far.

METHODS

The present study aimed to carry out in-vitro growth inhibitory efficacy studies of four novel drug molecules-SB239063, PD0332991 isethionate, FR180204 and apigenin, targeting different protein kinases of T. equi. A continuous microaerophilic stationary-phase culture (MASP) system was established for propagation of T. equi parasites. This in-vitro culture technique was used to assess the growth inhibitory effect of protein kinase targeted drug molecules, whereas diminazene aceturate was taken as control drug against T. equi. The inhibitory concentration (IC₅₀) was determined for comparative analysis. The potential cytotoxicity of the drug molecule was also assessed on horse's peripheral blood mononuclear cells (PBMCs) cell line.

RESULTS

SB239063 and diminazene aceturate drugs significantly inhibited (p < 0.05) the in-vitro growth of T. equi parasite at 0.1 µM, 1 µM, 10 µM, 50 µM and 100 µM concentration at ≥ 48 h of incubation period and respective IC₅₀ values were 4.25 µM and 1.23 µM. Furthermore, SB239063 was not cytotoxic to the horse PBMCs and found safer than diminazine aceturate drug. PD0332991 isethionate and FR180204 are extracellular signal-regulated kinase (ERK) inhibitors and significantly (p < 0.05) inhibited T. equi in-vitro growth at higher concentrations (≥ 48 h of incubation period) with respective IC₅₀ value of 10.41 µM and 21.0 µM. Lower concentrations of these two drugs were not effective (p > 0.05) even after 96 h of treatment period. Apigenin (protein kinase-C inhibitor) drug molecule was unsuccessful in inhibiting the T. equi parasite growth completely. After 96 h of in-vitro treatment period, a parasite viability study was performed on drug-treated T. equi parasitized RBCs. These drugs-treated parasitized RBCs were collected and transferred to wells containing fresh culture media (without drug) and naïve host RBCs. Drug-treated RBCs collected from SB239063, PD0332991, diminazene aceturate treatment (1 µM to 100 µM concentration) were unsuccessful in growing/multiplying further. Apigenin drug-treated T. equi parasites were live after 96 h of treatment.

CONCLUSION

It may be concluded that SB239063 was the most effective drug molecule (being lowest in IC₅₀ value) out of the four different protein kinase inhibitors tested in this study. This drug molecule has insignificant cytotoxic activity against horse's PBMCs.

Activities of artesunate-based combinations and tafenoquine against Babesia bovis in vitro and Babesia microti in vivo

BACKGROUND

Babesiosis represents a veterinary and medical threat, with a need for novel drugs. Artemisinin-based combination therapies (ACT) have been successfully implemented for malaria, a human disease caused by related parasites, Plasmodium spp. The aim of this study was to investigate whether ACT is active against Babesia in vitro and in vivo.

METHODS

Mefloquine, tafenoquine, primaquine, methylene blue and lumefantrine, alone or in combination with artesunate, were tested in vitro against Babesia bovis. Parasite growth was verified using a SYBR green I-based fluorescence assay. Mice infected with Babesia microti were treated with mefloquine or tafenoquine, alone or in combination with artesunate, and parasitemia was verified by microscopy and PCR.

RESULTS

All drugs, except lumefantrine, showed in vitro activity against B. bovis, with methylene blue showing the most potent activity (concentration 0.2 μM). Combination with artesunate led to improved activity, with mefloquine showing a striking 20-fold increase in activity. Tafenoquine (10 mg/kg, base), combined or not with artesunate, but not mefloquine, induced rapid clearance of B. microti in vivo by microscopy, but mice remained PCR-positive. Blood from mice treated with tafenoquine alone, but not with tafenoquine-artesunate, was infective for naive mice upon sub-inoculation.

CONCLUSIONS

Tafenoquine, and most likely other 8-aminoquinoline compounds, are promising compounds for the development of ACT for babesiosis.

Effect of Artesunate on Leishmania Amazonesis Induced Neuroinflammation and Nociceptive Behavior in Male Balb/C Mice

Simple Summary

Leishmaniasis is a multisystemic zoonotic disease with several symptoms, and treating this disease is a great challenge for veterinary medicine. Artemisinin derivatives are currently the most widely used drugs for the treatment of malaria, especially for their excellent safety profile and low cost. Artesunate is a more stable derivative of its precursor, artemisin, and has been shown to be a pluripotent agent with different pharmacological actions. In this study, we evaluated the role of neuroinflammation in leishmaniasis and its correlation with pain and sickness behavior, and the anti-inflammatory and neuroprotective effects of artesunate in a murine model of Leishmania amazonensis infection in BALB/c mice. The results from this study indicate that artesunate is a good candidate for treatment and/or as an adjuvant in anti- leishmaniasis therapy, and for preventing and alleviating leishmaniasis-induced pain and neuroinflammation.

Abstract

Background: Leishmaniasis is a multisystemic zoonotic disease with several symptoms, including neurological disorders. Leishmaniasis is accompanied by an increase in nociceptive behaviors, linked to the presence of a chronic inflammatory state, in both peripheral tissue and the central nervous system. Artesunate is a more stable derivative of its precursor artemisin and has been shown to be a pluripotent agent with different pharmacological actions. Methods: In this study, we investigated the effects of artesunate in Leishmaniaamazonensi- infected BALB/c mice, evaluating its effectiveness in reducing inflammation, neuroinflammation, and nociceptive and sickness behaviors. Results: Our results demonstrate a significant increase in pain sensitivity and sickness behaviors after L. amazonensis infection. Moreover, the infection induced a significant increase in inflammatory response at both the paw and spinal cord level. Treatment with artesunate was able to induce a significant decrease in tissue inflammation and neuroinflammation and thus induce a significant decrease in pain sensitivity and sickness behaviors. Conclusions: The results from this study indicate that artesunate is a good candidate for treatment and/or as an adjuvant in leishmanicidal therapy, and to prevent and alleviate leishmaniasis-induced pain and neuroinflammation and thereby improve the quality of life of leishmaniasis patients.

Exposure to ambient air causes degradation and decreased in vitro potency of buparvaquone and parvaquone

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Buparvaquone and parvaquone are used to treat livestock infected with Theileria spp.

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Air exposure had a significant impact on the stability of buparvaquone and parvaquone.

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Parvaquone was more stable than buparvaquone.

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Drug degradation was related with loss of potency by an in vitro viability assay.

Buparvaquone and parvaquone are hydroxynaphthoquinone compounds commonly used to treat livestock infected with Theileria species such as T. parva and T. annulata. In many (sub)tropical regions, chromatic changes in medicines can result from extreme environmental conditions and improper drug storage or handling, raising the possibility of drug degradation and loss of potency. We evaluated the effects of UV light, elevated temperature, and atmospheric air on the stability and potency of both buparvaquone and parvaquone by using a combination of high performance liquid chromatography (HPLC) and a T. equi based in vitro parasite growth inhibition assay (to measure potency). Aliquots (1 ml; 3 replicates per treatment) of each compound were subjected to a variety of treatments that varied in duration and intensity followed by HPLC and potency assays. Exposure to ambient air for 50 days was correlated with a significant loss of potency for both buparvaquone (4535%, P <  0.05) and parvaquone (247%, P <  0.05), while elevated temperature (37°C) and UV light exposure (24 h) had no significant impact (P >  0.05). The decrease in potency of both buparvaquone and parvaquone correlated with drug degradation (r = -0.74 and -0.88, respectively) as measured by HPLC. In practice, if there is headspace present in the vial, then ambient air will invariably enter the vial and contribute to degradation of these compounds. Such degradation may contribute to increasing drug resistance, economic losses for farmers, and animal welfare concerns for animals that are treated for Theileria infections.

Lumefantrine and o-choline - Parasite metabolism specific drug molecules inhibited in vitro growth of Theileria equi and Babesia caballi in MASP culture system

Theileria equi and Babesia caballi are tick-borne apicomplexan haemoprotozoan parasites of equines and are responsible for considerable economic losses to stakeholders. Chemotherapeutic drugs that are available not only require multiple dosages but also prompt multiple organ toxicity in treated host though incapable of clearing parasitaemia completely. In this study, we have screened the in vitro inhibitory efficacy of four different drug molecules (o-choline, DABCO®, lumefantrine and eugenol) against T. equi and B. caballi, targeting different parasite metabolism pathways. Imidocarb dipropionate and diminazene aceturate were used as reference control drugs. The 50% in vitro growth inhibitory concentration (IC₅₀) of lumefantrine, o-choline, DABCO® and eugenol for T. equi were: 30.90 μM; 84.38 μM; 443 μM; 120 μM and for B. caballi growth inhibition were: 5.58 μM; 135.29 μM; 150 μM; 197.05 μM, respectively. Imidocarb dipropionate inhibited the in vitro growth of T. equi at IC₅₀ of 257.5 nM, while diminazene aceturate inhibited the in vitro growth of B. caballi at IC₅₀ of 22 nM. DABCO® and eugenol were not so effective in inhibiting the in vitro growth of T. equi and B. caballi, while lumefantrine and o-choline significantly (p ≤ 0.05) inhibited the in vitro growth of these piroplasms targeting haem digestion and parasite membrane phospholipid synthesis.

A comprehensive review on past, present and future aspects of canine theileriosis

Canine theileriosis is a notorious tick borne piroplasmid infection of wild and domestic canines. The causative agent has not yet been accurately classified. PCR studies revealed that causative agent resembles to Theileria genus and thus provisionally named as Theileria annae. The other Theileria species reported in canines is Theileria annulata, Theileria equi and unnamed Theileria specie. This emergent canine infection is considered to be endemic in most of the European countries. However in Asia this disease has not been reported till date. The vectors responsible for transmission of this disease have not been determined. It has been suggested that DNA of Theileria annae has been detected in hard tick Ixodes hexagonus in Northwestern Spain and several other tick species. Clinically canine theileriosis is characterized by severe weakness, fever, hemoglobinuria and anemia. Recently atovaquone or buparvaquone plus azithromycin therapy showed better clinical efficacy. This comprehensive review is intended to summarize the current knowledge on prevalence and epidemiology of canine theileriosis in different countries of the world and associated tick vectors.

Efficacy, safety and tolerance of imidocarb dipropionate versus atovaquone or buparvaquone plus azithromycin used to treat sick dogs naturally infected with the Babesia microti-like piroplasm

BACKGROUND

Piroplasmosis caused by the Babesia microti-like piroplasm (Bml) is increasingly being detected in dogs in Europe. Sick dogs show acute disease with severe anaemia associated with thrombocytopenia with a poor response to current available drugs. This study assesses the safety and tolerance of three treatments and compares their efficacy over a full year of follow up in dogs naturally infected with Bml.

METHODS

Fifty-nine dogs naturally infected with Bml were randomly assigned to a treatment group: imidocarb dipropionate (5 mg/kg SC, 2 doses 14 d apart) (IMI); atovaquone (13.3 mg/kg PO q 8 h, 10 d)/azithromycin (10 mg/kg PO q 24 h, 10 d) (ATO); or buparvaquone (5 mg/kg IM, 2 d apart)/azithromycin (same dosage) (BUP). Before and after treatment (days 15, 45, 90 and 360), all dogs underwent a physical exam, blood tests and parasite detection (blood cytology and PCR). Clinical efficacy was assessed by grading 24 clinical and 8 clinicopathological signs from low to high severity.

RESULTS

Before treatment, most dogs had severe regenerative anaemia (88.13%) and thrombocytopenia (71.4%). On treatment Day 45, clinical signs were mostly reduced in all dogs, and by Day 90, practically all dogs under the ATO or BUP regimen were clinically healthy (76.4 and 88%, respectively). Highest percentage reductions in laboratory abnormalities (82.04%) were detected in animals treated with ATO. Over the year, clinical relapse of Bml was observed in 8 dogs (8/17) treated with IMI. However, on Day 360, these animals had recovered clinically, though clinicopathological abnormalities were still present in some of them. Parasitaemia was PCR-confirmed on Days 90 and 360 in 47.05 and 50% of dogs treated with ATO, 68 and 60.08% with BUP, and 94.1 and 73.3% with IMI, respectively. Even after 360 days, 13.3% of the dogs treated with IMI returned a positive blood cytology result.

CONCLUSIONS

IMI showed the worse clinical and parasitological, efficacy such that its use to treat Bml infection in dogs is not recommended. The treatments ATO and BUP showed better efficacy, though they were still incapable to completely eliminate PCR-proven infection at the recommended dose. All three treatments showed good tolerance and safety with scarce adverse events observed.

Extended-spectrum antiprotozoal bumped kinase inhibitors: A review

Many life-cycle processes in parasites are regulated by protein phosphorylation. Hence, disruption of essential protein kinase function has been explored for therapy of parasitic diseases. However, the difficulty of inhibiting parasite protein kinases to the exclusion of host orthologues poses a practical challenge. A possible path around this difficulty is the use of bumped kinase inhibitors for targeting calcium-dependent protein kinases that contain atypically small gatekeeper residues and are crucial for pathogenic apicomplexan parasites' survival and proliferation. In this article, we review efficacy against the kinase target, parasite growth in vitro, and in animal infection models, as well as the relevant pharmacokinetic and safety parameters of bumped kinase inhibitors.

Artemisinin and its derivatives in treating protozoan infections beyond malaria

Parasitic protozoan diseases continue to rank among the world's greatest global health problems, which are also common among poor populations. Currently available drugs for treatment present drawbacks, urging the need for more effective, safer, and cheaper drugs. Artemisinin (ART) and its derivatives are some of the most important classes of antimalarial agents originally derived from Artemisia annua L. However, besides the outstanding antimalarial and antischistosomal activities, ART and its derivatives also possess activities against other parasitic protozoa. In this paper we review the activities of ART and its derivatives against protozoan parasites in vitro and in vivo, including Leishmania spp., Trypanosoma spp., Toxoplasma gondii, Neospora caninum, Eimeria tenella, Acanthamoeba castellanii, Naegleria fowleri, Cryptosporidium parvum, Giardia lamblia, and Babesia spp. We conclude that ART and its derivatives may be good alternatives for treating other non-malarial protozoan infections in developing countries, although more studies are necessary before they can be applied clinically.

Development of a technique for standing hand-assisted laparoscopic splenectomy in five horses

OBJECTIVES

To develop an experimental standing hand-assisted laparoscopic splenectomy (HALS) technique, report the associated peri-operative complications and document the short-term surgical outcomes.

METHODS AND RESULTS

Five healthy 300-470 kg horses that underwent standing HALS. Spleens of different weights (2.25-7.0 kg) were removed using this technique. The main complication during surgery was difficulty sectioning the gastrosplenic ligament. The postoperative complications included adhesions of the colon to the nephrosplenic ligament stump and incisional discharge in two horses.

CONCLUSIONS

Standing HALS is a feasible experimental procedure for medium-sized horses, which avoids rib excision and general anaesthesia, but requires further development.

Clinical investigation on Theileria equi and Babesia caballi infections in Italian donkeys

BACKGROUND

Interest in the welfare and diseases of donkeys is constantly increasing in several countries. Despite this, clinical research into donkeys needs to be in continual development since they show different reactions compared to horses in many conditions, including infectious diseases, and need specific clinical and therapeutic approaches. No reports are currently available on clinical and clinical pathology data regarding donkeys with natural piroplasms infection.

RESULTS

Venous blood samples were taken from one hundred and thirty eight donkeys and underwent indirect fluorescent antibody test (IFAT) to detect IgG antibodies against Theileria equi and Babesia caballi and real-time polimerase chain reaction (PCR) to detect Babesia spp. and Theileria spp. Clinical examinations, haematological analyses and serum bilirubin evaluation were also performed and compared with positive or negative status. A seroprevalence of 40.6% and 47.8% was found for T. equi and B. caballi, respectively; double positivity was detected in 19.6% of the animals. PCR results showed that 17.4% of the animals tested positive for T.equi and 3.6% for B. caballi with no double positivity. Twelve donkeys (8.7%) had clinical signs consistent with chronic forms of the disease and no acute forms were detected. Fifty-eight donkeys had haematological and serum bilirubin alterations and 56 (96.6%) of them were IFAT and/or PCR positive. Changes in erythrocyte number, packed cell volume, hemoglobin concentration, mean corpuscular hemoglobin, platelets number and total bilirubin were significantly associated with positive and symptomatic animals.

CONCLUSION

Nonspecific clinical presentation seems to be very common in donkeys and several clinical pathology alterations persist after natural infection. Therefore, apparently healthy donkeys can have masked but severe clinical pathology alterations. Acute forms are very seldom observed in donkeys. Clinical monitoring of chronically infected donkeys is recommended since such animals represent a risk both for transmission to other animals and for their own health; furthermore, their production performances could be reduced. The study should also be intended as a contribution for veterinary practitioners because it describes the most usual clinical presentations and laboratory findings of equine piroplasmosis in naturally infected donkeys in endemic areas.

Towards identifying novel anti-Eimeria agents: trace elements, vitamins, and plant-based natural products

Eimeriosis, a widespread infectious disease of livestock, is caused by coccidian protozoans of the genus Eimeria. These obligate intracellular parasites strike the digestive tract of their hosts and give rise to enormous economic losses, particularly in poultry, ruminants including cattle, and rabbit farming. Vaccination, though a rational prophylactic measure, has not yet been as successful as initially thought. Numerous broad-spectrum anti-coccidial drugs are currently in use for treatment and prophylactic control of eimeriosis. However, increasing concerns about parasite resistance, consumer health, and environmental safety of the commercial drugs warrant efforts to search for novel agents with anti-Eimeria activity. This review summarizes current approaches to prevent and treat eimeriosis such as vaccination and commercial drugs, as well as recent attempts to use dietary antioxidants as novel anti-Eimeria agents. In particular, the trace elements selenium and zinc, the vitamins A and E, and natural products extracted from garlic, barberry, pomegranate, sweet wormwood, and other plants are discussed. Several of these novel anti-Eimeria agents exhibit a protective role against oxidative stress that occurs not only in the intestine of Eimeria-infected animals, but also in their non-parasitized tissues, in particular, in the first-pass organ liver. Currently, it appears to be promising to identify safe combinations of low-cost natural products with high anti-Eimeria efficacy for a potential use as feed supplementation in animal farming.

Effects of Artemisia annua and Foeniculum vulgare on chickens highly infected with Eimeria tenella (phylum Apicomplexa)

Background

Intensive poultry production systems depend on chemoprophylaxis with anticoccidial drugs to combat infection. A floor-pen study was conducted to evaluate the anticoccidial effect of Artemisia annua and Foeniculum vulgare on Eimeria tenella infection. Five experimental groups were established: negative control (untreated, unchallenged); positive control (untreated, challenged); a group medicated with 125 ppm lasalocid and challenged; a group medicated with A. annua leaf powder at 1.5% in feed and challenged; and a group treated with the mixed oils of A. annua and Foeniculum vulgare in equal parts, 7.5% in water and challenged. The effects of A. annua and oil extract of A. annua + F. vulgare on E. tenella infection were assessed by clinical signs, mortality, fecal oocyst output, faeces, lesion score, weight gain, and feed conversion.

Results

Clinical signs were noticed only in three chickens from the lasalocid group, six from the A. annua group, and nine from the A. annua + F. vulgare group, but were present in 19 infected chickens from the positive control group. Bloody diarrhea was registered in only two chickens from A. annua group, but in 17 chickens from the positive control group. Mortality also occurred in the positive control group (7/20). Chickens treated with A. annua had a significant reduction in faecal oocysts (95.6%; P = 0.027) and in lesion score (56.3%; P = 0.005) when compared to the positive control. At the end of experiment, chickens treated with A. annua leaf powder had the highest body weight gain (68.2 g/day), after the negative control group, and the best feed conversion (1.85) among all experimental groups.

Conclusions

Our results suggest that A. annua leaf powder (Aa-p), at 1.5% of the daily diet post-infection, can be a valuable alternative for synthetic coccidiostats, such as lasalocid.

Artemisone inhibits in vitro and in vivo propagation of Babesia bovis and B. bigemina parasites

Artemisone was evaluated, in in vitro and in vivo, for control of bovine babesiosis caused by Babesia bigemina and Babesia bovis parasites. In vitro, artemisone reduced parasitemia in a dose-dependent manner: the inhibitory effects increased gradually, reaching a maximum inhibition of 99.6% and 86.4% for B. bigemina and B. bovis, respectively 72 h after initiation of treatment with initial parasitemia of 0.5%. In calves infected with either B. bigemina or B. bovis artemisone treatment was well tolerated and prevented development of acute babesiosis in all animals except for one B. bovis-infected calf. The treatment did not eliminate all blood parasites, and recovered animals carried a persistent low-level infection. Treatment with artemisone may be useful as an alternative drug for preventing the pathology that results from babesiosis, without interfering with acquired immune protection following recovery from an acute babesiosis infection or vaccination.

Review of equine piroplasmosis

Equine piroplasmosis is caused by one of 2 erythrocytic parasites Babesia caballi or Theileria equi. Although the genus of the latter remains controversial, the most recent designation, Theileria, is utilized in this review. Shared pathogenesis includes tick-borne transmission and erythrolysis leading to anemia as the primary clinical outcome. Although both parasites are able to persist indefinitely in their equid hosts, thus far, only B. caballi transmits across tick generations. Pathogenesis further diverges after transmission to equids in that B. caballi immediately infects erythrocytes, whereas T.equi infects peripheral blood mononuclear cells. The recent re-emergence of T.equi in the United States has increased awareness of these tick-borne pathogens, especially in terms of diagnosis and control. This review focuses in part on factors leading to the re-emergence of infection and disease of these globally important pathogens.

Re-emergence of the apicomplexan Theileria equi in the United States: elimination of persistent infection and transmission risk

Arthropod-borne apicomplexan pathogens that cause asymptomatic persistent infections present a significant challenge due to their life-long transmission potential. Although anti-microbials have been used to ameliorate acute disease in animals and humans, chemotherapeutic efficacy for apicomplexan pathogen elimination from a persistently infected host and removal of transmission risk is largely unconfirmed. The recent re-emergence of the apicomplexan Theileria equi in U.S. horses prompted testing whether imidocarb dipropionate was able to eliminate T. equi from naturally infected horses and remove transmission risk. Following imidocarb treatment, levels of T. equi declined from a mean of 10^4.9 organisms/ml of blood to undetectable by nested PCR in 24 of 25 naturally infected horses. Further, blood transfer from treated horses that became nested PCR negative failed to transmit to naïve splenectomized horses. Although these results were consistent with elimination of infection in 24 of 25 horses, T. equi-specific antibodies persisted in the majority of imidocarb treated horses. Imidocarb treatment was unsuccessful in one horse which remained infected as measured by nested PCR and retained the ability to infect a naïve recipient via intravenous blood transfer. However, a second round of treatment eliminated T. equi infection. These results support the utility of imidocarb chemotherapy for assistance in the control and eradication of this tick-borne pathogen. Successful imidocarb dipropionate treatment of persistently infected horses provides a tool to aid the global equine industry by removing transmission risk associated with infection and facilitating international movement of equids between endemic and non-endemic regions.

The molecular mechanism of action of artemisinin--the debate continues

Despite international efforts to 'roll back malaria' the 2008 World Malaria Report revealed the disease still affects approximately 3 billion people in 109 countries; 45 within the WHO African region. The latest report however does provide some 'cautious optimism'; more than one third of malarious countries have documented greater than 50% reductions in malaria cases in 2008 compared to 2000. The goal of the Member States at the World Health Assembly and 'Roll Back Malaria' (RBM) partnership is to reduce the numbers of malaria cases and deaths recorded in 2000 by 50% or more by the end of 2010. Although malaria is preventable it is most prevalent in poorer countries where prevention is difficult and prophylaxis is generally not an option. The burden of disease has increased by the emergence of multi drug resistant (MDR) parasites which threatens the use of established and cost effective antimalarial agents. After a major change in treatment policies, artemisinins are now the frontline treatment to aid rapid clearance of parasitaemia and quick resolution of symptoms. Since artemisinin and its derivatives are eliminated rapidly, artemisinin combination therapies (ACT's) are now recommended to delay resistance mechanisms. In spite of these precautionary measures reduced susceptibility of parasites to the artemisinin-based component of ACT's has developed at the Thai-Cambodian border, a historical 'hot spot' for MDR parasite evolution and emergence. This development raises serious concerns for the future of the artemsinins and this is not helped by controversy related to the mode of action. Although a number of potential targets have been proposed the actual mechanism of action remains ambiguous. Interestingly, artemisinins have also shown potent and broad anticancer properties in cell lines and animal models and are becoming established as anti-schistosomal agents. In this review we will discuss the recent evidence explaining bioactivation and potential molecular targets in the chemotherapy of malaria and cancer.

Discovery, mechanisms of action and combination therapy of artemisinin

Despite great international efforts, malaria still inflicts an enormous toll on human lives, especially in Africa. Throughout history, antimalarial medicines have been one of the most powerful tools in malaria control. However, the acquisition and spread of parasite strains that are resistant to multiple antimalarial drugs have become one of the greatest challenges to malaria treatment, and are associated with the increase in morbidity and mortality in many malaria-endemic countries. To deal with this grave situation, artemisinin-based combinatory therapies (ACTs) have been introduced and widely deployed in malarious regions. Artemisinin is a new class of antimalarial compounds discovered by Chinese scientists from the sweet wormwood Artemisia annua. The potential development of resistance to artemisinins by Plasmodium falciparum threatens the usable lifespan of ACTs, and therefore is a subject of close surveillance and extensive research. Studies at the Thai-Cambodian border, a historical epicenter of multidrug resistance, have detected reduced susceptibility to artemisinins as manifested by prolonged parasite-clearance times, raising considerable concerns on resistance development. Despite this significance, there is still controversy on the mode of action of artemisinins. Although a number of potential cellular targets of artemisinins have been proposed, they remain to be verified experimentally. Here, we review the history of artemisinin discovery, discuss the mode of action and potential drug targets, and present strategies to elucidate resistance mechanisms.

Analysis of underivatized artemisinin and related sesquiterpene lactones by high-performance liquid chromatography with ultraviolet detection

INTRODUCTION

Although high-performance liquid chromatography with ultraviolet detection (HPLC-PAD) is widely available, it has not been used for artemisinin (1) analysis because of the lack of UV absorption reported for this lactone. Increased Artemisia annua cultivation for production of 1 requires an affordable and reliable method to analyse 1 and its precursors dihydroartemisinic acid (2) and artemisinic acid (3) simultaneously from underivatized plant extracts.

OBJECTIVE

To validate HPLC-PAD for the quantification of underivatized artemisinin from A. annua and artemisinin-based drugs.

METHODOLOGY

Dried A. annua leaves were extracted with petroleum ether, dried, reconstituted in acetonitrile, and analysed by HPLC-PAD at 192 nm using an isocratic mobile phase (60:40, acetonitrile:0.1% acetic acid). HPLC-PAD was evaluated through accuracy, precision, recovery and comparison with HPLC with evaporative light scattering detection (HPLC-ELSD).

RESULTS

HPLC-PAD proved accurate, precise and reproducible for the direct quantification of 1 and related compounds, and was more sensitive than ELSD for most of the compounds tested. The limit of quantification of 1-3 from plants was 0.048, 0.024 and 0.008 g/100 g dry weight, respectively. Recoveries were over 98%, with good intra- and inter-day repeatability. HPLC-PAD correlated significantly (r(2 )= 0.99, p < 0.001) with HPLC-ELSD for artemisinin analysis. HPLC-PAD was also reliable for the analysis of dihydroartemisinin, artesunate and artelinic acid.

CONCLUSION

HPLC with ultraviolet detection was validated for the quantification of underivatized 1, 2, and 3 from crude plant samples, and is readily applicable for the quality control of herbals and artemisinin-related pharmaceutical compounds.

Affordable and sensitive determination of artemisinin in Artemisia annua L. by gas chromatography with electron-capture detection

Artemisinin demand has increased sharply since the World Health Organization recommended its use as part of the artemisinin combination therapies in 2001. The area for the crop cultivation has expanded in Africa and Asia and simpler and affordable methods for artemisinin analysis are needed for crop quality control. This work presented a novel chromatographic method of artemisinin analysis using gas chromatography with electron-capture detection. The sample extraction and preparation involved a single-solvent one-step extraction, with samples being analyzed in the extraction solvent directly after extraction. This method was accurate and reproducible with over 97% recoveries. The limit of detection was less than 3 microg/mL and the limit of quantification was less than 9 microg/mL, allowing samples as low as 100mg dry weight to be analyzed for artemisinin. The method can be applied to quality control of commercial plant extracts and to artemisinin-derived pharmaceuticals.

Nutrient deficiency in the production of artemisinin, dihydroartemisinic acid, and artemisinic acid in Artemisia annua L

Artemisia annua became a valuable agricultural crop after the World Health Organization recommended artemisinin as a component of ACT (artemisinin-combination based therapies) for malaria in 2001. A cloned, greenhouse-grown, A. annua (Artemis) subjected to an acidic soil and macronutrient deficit was evaluated for artemisinin production. Lack of lime (L) and macronutrients (N, P, and K) reduced leaf biomass accumulation. When L was provided (pH 5.1), the highest average leaf biomass was achieved with the "complete" (+N, +P, +K, and +L) treatment (70.3 g/plant), and the least biomass was achieved with the untreated (-N, -P, -K, and -L) treatment (6.18 g/plant). The nutrient least required for biomass accumulation per plant (g) was K (49.0 g), followed by P (36.5 g) and N (14.3 g). The artemisinin concentration (g/100 g) was significantly higher (75.5%) in -K plants when compared to plants under the complete treatment (1.62 vs 0.93%). Although the artemisinin total yield (g/plant) was 21% higher in -K plants, it was not significantly different from plants under the complete treatment (0.80 vs 0.66 g/plant). There were no marked treatment effects for concentration (g/100 g) or yield (g/plant) of both dihydroartemisinic acid and artemisinic acid, although higher levels were achieved in plants under the complete or -K treatments. There was a positive and significant correlation between artemisinin and both artemisinic acid and dihydroartemisin acid, in g/100 g and g/plant. This is the first report where potassium deficiency significantly increases the concentration (g/100 g) of artemisinin. Thus, under a mild potassium deficiency, A. annua farmers could achieve similar gains in artemisinin/ha, while saving on potassium fertilization, increasing the profitability of artemisinin production.

Current perspectives on the mechanism of action of artemisinins

Artemisinin derivatives are the most recent single drugs approved and introduced for public antimalarial treatment. Although their recommended use is for treatment of Plasmodium falciparum infection, these drugs also act against other parasites, as well as against tumor cells. The mechanisms of action attributed to artemisinin include interference with parasite transport proteins, disruption of parasite mitochondrial function, modulation of host immune function and inhibition of angiogenesis. Artemisinin combination therapies are currently the preferred treatment for malaria. These combinations may prevent the induction of parasite drug resistance. However, in view of the multiple mechanisms involved, especially when additional drugs are used, the combined therapy should be carefully examined for antagonistic effects. It is now a general theory that the crucial mechanism is interference with plasmodial SERCA. Therefore, future development of resistance may be associated with overproduction or mutations of this transporter. However, a general mechanism, such as alterations in general drug transport pathways, is feasible. In this article, we review the evidence for each mechanism of action suggested.